Sense of smell and obesity

A new study has found a link between sense of smell and obesity.  A recent review of this study concludes that people with obesity have a reduced ability to detect and discriminate smell compared with those who are not obese.
Woman using sense of smell while cooking
A recent review highlights a possible link between obesity and olfaction.

Obesity is a medical condition characterized by an excessive amount of body fat.

It is a global issue that affects millions of people worldwide, and it is a risk factor for diabetes and heart disease.

Doctors or nutritionists can identify obesity using the body mass index (BMI). The BMI is a diagnostic tool that assesses if a person is an appropriate weight for their age, sex, and height.

According to the World Health Organization (WHO), global obesity has nearly tripled since 1975.

In 2016, almost 2 billion adults were overweight, of which 650 million were obese. In the same year, 41 million children under 5 years old were overweight or obese.

In 2013, the American Medical Association (AMA) recognized obesity as a disease. The decision changed the way the medical community related to this complex issue. The ruling challenged the widespread idea that obesity is the direct consequence of eating too much and not doing enough physical activity. The AMA argued that “some people do not have complete control of their weight.”

Surprising link between weight and smell

The relationship between the sense of smell and body weight was a relatively unknown area of scientific study and knowledge, up until now. Researchers from the University of Otago in New Zealand recently discovered a surprising link between obesity and the ability to smell. The team published its findings in Obesity Reviews.

The study involved researchers from Otago’s Departments of Food Science, Anatomy, and Mathematics/Statistics. The scientists gathered scientific papers regarding the link between body weight and sense of smell. They also collected information of nearly 1,500 individuals from “empirical and clinical worldwide studies.”

“After compiling our evidence, we found there is, in fact, a strong link between a person’s body weight and their smell ability — the better a person can smell, the more likely the person is to be slim, or vice versa,” says Dr. Mei Peng, lead author of the study, from the University of Otago’s Department of Food Science.

Dr. Peng added that smell plays a critical role when it comes to eating behavior because it affects the way we identify and choose between different flavors. A poor sense of smell may result in people making unhealthful food choices, which can increase their risk of obesity.

For example, they might choose, or be more attracted to, saltier and tastier foods such as bacon and maple syrup instead of blander foods, such as low-fat cereal with less sugar.”

Dr. Mei Peng

Weight loss surgery could improve the sense of smell

The researchers found that people who were closer to obesity had a reduced ability to smell and identify odors. Based on these findings, the researchers hypothesized that obesity alters a person’s metabolism, which affects communication pathways between the gut and brain.

To re-establish the pathway between the gut and brain, researchers considered the effects of two surgical obesity treatments. They looked at stomach removal and gastric bypass (a surgical procedure which involves dividing the stomach into two pouches and rearranging the small intestine to connect to both).

The findings showed that stomach removal could improve the sense of smell, while other obesity surgeries do not have the same effect.

“Cutting the stomach could change nerves in the stomach that affect the gut-brain pathway, so smell changes could be the key to the difference between the two surgeries — essentially, the smaller size of the stomach might not be the factor that leads to weight loss, it is more likely due to the gut-brain pathway being reset,” Dr. Peng concludes.

Dr. Peng hopes that these findings will increase awareness around the critical relationship between eating habits and senses. This groundbreaking study could deepen our knowledge of the role that “reward-factor smell has in various body-shape groups.”

Tiny implants may boost weight loss

As obesity rates soar, tiny implants which modify digestive processes appear to be the new trend in controlling or reversing obesity. The hunt for innovative interventions using tiny implants is more pressing than ever. According to a recent paper, a tiny, battery-free implant could offer fresh hope.
tiny implants
Researchers Guang Yao (left) and Xudong Wang (right) hold the small implantable device.
Image credit: Sam Million-Weaver

Obesity is a growing concern; today, experts class well over one-third of people in the United States as obese.

Globally, an estimated 4 million people died of conditions related to a high body mass index (BMI) in 2015 alone.

These worrying trends mean scientists are focused on understanding the causes, risk factors, and implications of obesity.

The reason why obesity develops in certain people and not others is multifaceted, involving genetic, hormonal, and psychological factors, among others.

The direct cause of excess weight, however, is the ingestion of more calories than the body uses. Some scientists are trying to find ways to trick the brain into consuming less food.

New tiny implants technology

Recently, researchers from the University of Wisconsin-Madison tested a groundbreaking, high-tech solution.

The scientists designed a small, implantable device that they hope will reduce hunger pangs and help people lose weight.

The device, which is less than 1 centimeter across, can be implanted using a minimally invasive technique.

Consisting of a flexible nanogenerator, it sends small pulses of electricity through the vagus nerve, which passes messages between the stomach and the brain.

This mild stimulation convinces the brain that the stomach is full and reduces feelings of hunger.

Importantly, the device does not need a battery or charging. Instead, it gets its power from the churning motion of the stomach during peristalsis.

Because the movement of the stomach provides the device with its power, it only works when the arrival of food causes the stomach to move; this means that the device is only active at the precise time its signals will be effective.

“The pulses correlate with the stomach’s motions, enhancing a natural response to help control food intake,” explains author Xudong Wang, who is a professor of materials science and engineering.

To test the device, the researchers used a rat model, and they have published their findings in the journal Nature Communications. The results have encouraged the authors, as they explain:

We successfully demonstrated this strategy on rats and achieved 38 percent weight loss in as short as 15 days without further rebound, exceeding all current electrical stimulation approaches.”

No obvious safety issues

Importantly, the implant stayed in the correct position throughout the 12-week trial. Furthermore, there were no measurable negative impacts on the rats’ kidney or liver functions and no signs of infection.

The researchers carried out postmortem examinations on most of the animals’ vital organs and found no adverse effects.

When they compared the tiny implants with other weight-loss devices, it had several benefits. Gastric bypass surgery, for instance, permanently reduces the capacity of the stomach, whereas, the new implant is fully reversible, and the implant procedure is much less invasive.

This is not the only implant that stimulates the vagus nerve to reduce hunger pangs. There is a competitor that goes by the name of Maestro, which the U.S. Food and Drug Administration (FDA) has approved. However, Maestro requires ongoing maintenance and up to 3 hours of charging each week.

The new tiny implants have no battery or wiring, as Wang explains, “It’s automatically responsive to our body function, producing stimulation when needed. Our body knows best.”

Also, Maestro uses high-frequency jolts to completely shut down the vagus nerve, rather than the intermittent pulsing of the new technology. Because the newer implant only works when it needs to, the body is less likely to overcompensate, which, in the case of Maestro, can slowly reduce how effective it is over time.

Of course, there is a long path between here and use in humans, but the authors are keen to continue their investigations. Next, they plan to trial the device in larger animals.

New Obesity procedure

New obesity procedure appears to also reduce muscle mass.  A study about a new obesity procedure for the treatment of obesity has raised some concerns. This is because, while the treatment leads to weight loss, the pounds a person sheds consist of skeletal muscle as well as fat. Also, body fat loss seems to be mainly of the subcutaneous — as opposed to the riskier visceral — type.
obesity procedure doctor taking measurements of obese man
Visceral fat can harm health, and some people with obesity resort to surgical procedures to remove it.

Skeletal muscle is necessary for good health; its loss can result in not only physical problems, but it can also impair metabolism and raise the risk of injury.

Visceral fat is the type of fat that surrounds the organs deep inside the abdomen. Doctors have linked carrying too much of it to health problems, such as type 2 diabetes and heart disease.

The new obesity procedure is called left gastric artery embolization. Interventional radiologists have been using it for decades to stop bleeding in emergencies.

However, the idea of using gastric artery embolization to treat obesity is new, and clinical trials are currently evaluating its safety and effectiveness for such a purpose.

The aim of the new obesity procedure treatment is to reduce the effect of an appetite hormone by injecting microscopic beads to block an artery that supplies blood to the stomach.

The study’s findings featured recently at the annual meeting of the Radiological Society of North America that is currently taking place in Chicago, IL.

Need for new cost-effective, low-risk obesity procedures

Study lead author Dr. Edwin A. Takahashi, who is a vascular and interventional radiology fellow at the Mayo Clinic in Rochester, MN, explains that a lot of research has shown that gastric artery embolization can achieve weight loss.

“However,” he adds, “there has been no data on what is contributing to the weight loss, whether the patients are losing fat, as desired, or muscle mass, or some combination of the two.”

Obesity is a significant global public health issue with links to heart disease, type 2 diabetes, cancer, and other serious illnesses and health problems.

Rates of obesity and being overweight have almost tripled worldwide over the last 40 years, according to the World Health Organization (WHO).

The WHO estimates for 2016 suggest that being overweight affects more than 1.9 billion of the world’s adults. This figure includes some 650 million adults with obesity.

While changes to lifestyle factors such as diet and physical activity can work, for many people, these are not enough, and they opt to undergo weight-loss operations that reduce the size of the stomach.

Such surgical procedures have proved effective as treatments for obesity, but they are costly and carry risks and complications.

Left gastric artery embolization

Left gastric artery embolization — if found to be effective and safe — could offer people a less invasive option for the treatment of obesity.

The obesity procedure involves injecting microscopic beads into the artery that delivers blood to the stomach. The radiologist inserts a catheter either in the wrist or groin and uses imaging to reach the artery.

Once released into the artery, the microbeads block the flow of blood through the smaller blood vessels to the stomach. This has the effect of reducing production of ghrelin, a hunger-stimulating hormone.

Early trials have shown promising results that the procedure can help people lose weight. However, there is little information about where the weight loss comes from, and how it affects body composition of fat and muscle.

Dr. Takahashi and his team examined computed tomography scans of 16 overweight people, some with obesity, who had undergone left gastric artery embolization to stop bleeding.

With help from special software that analyzes tissue density, they assessed fat and muscle composition on scans taken before and about 1.5 months after the treatment.

Results raised some concerns by new obesity procedure

All 16 of the individuals who underwent embolization lost a significant amount of weight afterward. On average, they lost 6.4 percent of their body weight in the ensuing 1.5 months.

Their body mass index (BMI) fell by 6.3 percent over the same period.

The weight loss came as no surprise to the researchers; however, what did surprise them was the alteration in body composition.

They calculated that skeletal muscle index reduced by 6.8 percent. This index reflects the quantity of muscle in the body that is attached to bone and helps the movement of limbs and other body parts.

Loss of skeletal muscle can not only reduce physical function, but it can also damage metabolism and raise the risk of injury.

“The significant decrease in the amount of skeletal muscle,” says Dr. Takahashi, “highlights the fact that patients who undergo this procedure are at risk for losing muscle mass and need to be managed accordingly after [the] procedure.”

We must make sure they receive adequate nutrition to minimize the amount of muscle tissue they lose.”

Dr. Edwin A. Takahashi

The results also showed that the individuals lost a lot of body fat; there was an average drop of 3.7 percent in body fat index.

However, most of the body fat loss was due to the reduction in subcutaneous fat. Loss of visceral fat was insignificant over the follow-up.

Subcutaneous fat is all over the body under the skin. Visceral fat is fat that surrounds the organs deep in the abdominal cavity.

Science “has been distinctly linked” carrying excessive amounts of visceral fat to several health problems and conditions. These include impaired metabolism, insulin resistance, increased risk to certain cancers, prolonged hospitalization, and higher risk of complications.

The team now want to focus further studies on individuals who undergo left gastric artery embolization specifically to treat obesity.

Low-carb diet and permanent weight loss

Low-carb diet can help you lose weight and keep it off permanently.
“The largest and longest feeding study to test the ‘carbohydrate-insulin model'” concludes that a lower carb intake burns more calories, which may help people maintain weight loss over a longer period of time.
person eating a steak with low carb diet
Eating a high-quality, low-carb diet may help us stave off weight gain for longer.

Cara Ebbeling, Ph.D., together with Dr. David Ludwig — both at Boston Children’s Hospital in Massachusetts — led the new study, which now appears in the BMJ.

As they explain, when we lose weight, the body adapts by lowering its energy expenditure. In other words, it burns fewer calories.

This way, the metabolism protects itself against long-term weight changes.    Low-carb diet can help lose weight permanently

However, when the weight loss is intentional, this adaptive response can be frustrating for dieters, as it leads to weight regain.

Although weight gain after dieting is a well-known phenomenon, researchers do not know much about how different diets affect the way the metabolism responds to them.

The so-called carbohydrate-insulin model, however, suggests one such mechanism. It posits that highly processed foods high in sugar drive hormonal changes that increase the appetite and lead to weight gain.

“According to this model,” explains Dr. Ludwig, “the processed carbohydrates that flooded our diets during the low-fat era have raised insulin levels, driving fat cells to store excessive calories. With fewer calories available to the rest of the body, hunger increases and metabolism slows — a recipe for weight gain.”

In this context, Ebbeling, Dr. Ludwig, and their colleagues decided to investigate the effects that different diets had on the metabolism. Specifically, they looked at the carb-to-fat ratio in varying diets over a 20-week period.

Studying carb intake, weight, and calories in low-carb diet

The researchers examined the effect of different diets on 234 adults aged 18–65 whose body mass index (BMI) was at least 25. As part of the study, the participants had also adhered to a weight loss plan for 10 weeks.

By the end of the trial, 164 participants had achieved their weight loss goal of around 12 percent of their total weight. Then, they adhered to either a high-, moderate-, or low-carb diet for 20 weeks, allowing the researchers to examine if they managed to maintain the weight loss.

The high-carb diet was composed of 60 percent high-quality carbs, the moderate-carb one had 40 percent carbs, and the low-carb diet had 20 percent carbs. The diets also minimized sugar intake and used whole grains.

During this time, the scientists measured the participants’ weight and tracked the number of calories they burned. They also examined the participants’ insulin secretion and metabolic hormones.

‘A 20-pound weight loss after 3 years’

At the end of the study period, people in the low-carb group burned significantly more calories than those who had been on a high-carb diet.

Specifically, participants who were on a low-carb diet burned around 250 kilocalories more per day than those who were on a high-carb diet.

Ebbeling explains, “If this difference persists — and we saw no drop-off during the 20 weeks of our study — the effect would translate into about a 20-pound weight loss after 3 years, with no change in calorie intake.”

The results also indicated that for participants who had the highest insulin secretion, the impact of a low-carb diet was even more significant: low-carb dieters burned 400 calories more per day than high-carb dieters.

“A low glycemic load, high-fat diet,” explain the authors, “might facilitate weight loss maintenance beyond the conventional focus on restricting energy intake and encouraging physical activity.”

Ebbeling says, “Our observations challenge the belief that all calories are the same to the body.”

This is the largest and longest feeding study to test the ‘carbohydrate-insulin model,’ which provides a new way to think about and treat obesity.”

Dr. David Ludwig

Obesity versus Depression

Is depression the cause of obesity or is obesity the cause of depression? Although depression and obesity often come hand in hand, the relationship between the two is difficult to tease apart. A new, large-scale genomic study adds new evidence.

Pensive woman ponders obesity
The relationship between depression and obesity is complex.

Both excessive weight and depression are significant global health problems. According to the authors of the latest research, they cost the global economy trillions of dollars every year.

Previous studies have noted that depression often appears in individuals who are overweight or obese.

However, observational studies have not been able to demonstrate whether obesity causes depression, as there are many competing factors to consider.

For instance, being grossly overweight is a risk factor for a number of conditions, and so it might be that dealing with other health issues increases the likelihood of becoming depressed, rather than the obesity being the cause.

Some researchers have argued that the relationship might be the other way around: depression is a risk for obesity.

Others believe that depression and obesity exacerbate each other. For instance, obesity might make depression more likely to occur initially, but once depressive symptoms arise, they might compound the condition by making it harder for the individual to exercise. In these cases motivation of the individual would be a great place to start.

Obesity and depression revisited

To gain a better understanding of this complicated relationship, researchers from the University of Exeter in the United Kingdom joined forces with scientists from the University of South Australia. They published their results in the International Journal of Epidemiology this week.

“Obesity and depression are both global health problems that have a major impact on lives and are costly to health services,” explains lead author Dr. Jess Tyrrell. “We’ve long known there’s a link between the two, yet it’s unclear whether obesity causes depression or vice versa, and also whether it’s being overweight in itself or the associated health problems that can cause depression.”

The study used genetic data to inspect the causal relationship between excessive weight and depression. The team wanted to understand whether a higher body mass index (BMI) was related to an increased risk of depression without the presence of other health conditions.

The researchers used genetic and medical data from 48,000 people with depression and compared it with in excess of 290,000 controls, making it the largest study to address this question to date.

Psychological impact to blame?

Overall, as expected, a higher BMI was associated with higher odds of depression. This association was stronger in women than men, confirming earlier findings. Women with a high BMI had a 21 percent increase in risk, compared with 8 percent in men.

By investigating individuals with genes predisposing them to obesity but without ones that predispose them to metabolic conditions, such as diabetes — referred to as a “favorable metabolic profile” — the researchers could separate out the psychological component of obesity.

In their analysis, they accounted for a range of variables that could influence the results, including socioeconomic position, alcohol consumption, smoking, and physical activity.

They found that individuals with a favorable metabolic profile were just as likely to develop depression as individuals with obesity that carried genes predisposing them to develop metabolic conditions. This effect was most pronounced in women.

To double-check their findings, they also took data from the Psychiatric Genomics Consortium. And their second analysis returned similar results, adding further weight to their conclusions.

“Our robust genetic analysis concludes that the psychological impact of being obese is likely to cause depression.” Dr. Jess Tyrrell

These results provide vital insight, as Dr. Tyrrell explains, “This is important to help target efforts to reduce depression, which makes it much harder for people to adopt [healthful] lifestyle habits.”

However, the relationship between the two is convoluted, and questions remain. As the authors write, “we have not ruled [out] a possible bidirectional causal relationship between higher BMI and depression […] Further research is required to explore the causal role of depression on body mass index and obesity.”

Because depression and obesity can have profound impacts on individuals and society at large, scientific attention is likely to continue to look at their links.

Body Mass Index Measurement

This post deals with measuring Body Mass Index (BMI) for adults, children, and teens. Body mass index, or BMI, is a measure of body size. It combines a person’s weight with their height. The results of a BMI measurement can give an idea about whether a person has the correct weight for their height. 

BMI (Body Mass Index) is a screening tool that can indicate whether a person is underweight or if they have a healthy weight, excess weight, or obesity. If a person’s Body Mass Index is outside of the healthy range, their health risks may increase significantly.

Carrying too much weight can lead to a variety of health conditions, such as type 2 diabetes, high blood pressure, and cardiovascular problems.  In a previous post, we offered five simple exercises which can help a person achieve some of their weight goals.

A weigh that is too low can increase the risk of malnutrition, osteoporosis, and anemia. The doctor will make suitable recommendations.

Body Mass Index does not measure body fat directly, and it does not account for age, sex, ethnicity, or muscle mass in adults.

However, it uses standard weight status categories that can help doctors to track weight status across populations and identify potential issues in individuals.

BMI (Body Mass Index) in adults

Body Mass Index calculator shows healthy weight
A BMI chart or calculator can show a person if they have a healthy weight.

Calculating BMI involves measuring a person’s height and body weight.

 

Metric

  • To calculate BMI in metric units, use the following method: BMI = kg/m2
  • So, to calculate an adult’s BMI: Divide their weight in kilograms (kg) by the square of their height in meters (m2)

Since most people measure height in centimeters (cm), divide height in cm by 100 to get height in meters.

Imperial

  • When using imperial units, the formula is: BMI = lbs x 703/in2
  • In other words: Multiply a person’s weight in pounds (lbs) by 703. Then divide by their height in inches, squared (in2)

To avoid using the math, a person can use a calculator or a chart to find their BMI.

BMI calculator

Enter height or weight in either imperial or metric measurements to find your BMI.

1) Metric BMI Calculator

2) Imperial BMI Calculator

BMI charts

People can also work out their BMI using a chart. Click here to see a chart provided by the National Heart, Lung, and Blood Institute (NHLBI).

Locate your height in inches on the side of the chart, then look across to find your body weight in pounds. Scan to the top to see if the result corresponds to a normal weight, overweight, or obesity.

Understanding the results

The following table shows the standard weight status categories associated with BMI ranges for adults.

BMI Weight status
Below 18.5 Underweight
18.5–24.9 Healthy
25.0–29.9 Overweight
30.0 and above Obese

BMI of less than 18.5

A BMI of less than 18.5 indicates that you are underweight, so you may need to put on some weight. You are recommended to ask your doctor or a dietitian for advice.

BMI of 18.5–24.9

A BMI of 18.5-24.9 indicates that you are at a healthy weight for your height. By maintaining a healthy weight, you lower your risk of developing serious health problems.

BMI of 25–29.9

A BMI of 25-29.9 indicates that you are slightly overweight. You may be advised to lose some weight for health reasons. You are recommended to talk to your doctor or a dietitian for advice.

BMI of over 30

A BMI of over 30 indicates that you are heavily overweight. Your health may be at risk if you do not lose weight. You are recommended to talk to your doctor or a dietitian for advice.

BMI in children and teens

In adults, BMI values are not linked to age and are the same for both sexes.

However, measuring Body Mass Index in children and teens is slightly different. Girls and boys develop at different rates and have different amounts of body fat at different ages. For this reason, BMI measurements during childhood and adolescence take age and sex into consideration.

Doctors and other health professionals do not categorize children by healthy weight ranges because:

  • they change with each month of age
  • male and female body types change at different rates
  • they change as the child grows taller

Doctors calculate BMI for children and teens in the same way as they do for adults, by measuring height and weight. Then they locate the BMI number and person’s age on a sex-specific BMI-for-age chart. This will indicate whether the child is within a healthy range.

Calculator and charts for child and teen Body Mass Index

The Centers for Disease Control and Prevention (CDC) have produced a calculator that provides BMI and the corresponding BMI-for-age percentile on a CDC growth chart for children and teens.

First, click here for the calculator.

Next, use the charts to see if a child’s weight is suitable for their age.

Click here for the charts:

What do the results mean?

The following categories explain the meaning of the results:

Weight status category Percentile range
Underweight Below the 5th percentile
Healthy weight 5th percentile to less than the 85th percentile
Overweight 85th to less than the 95th percentile
Obesity Equal to or greater than the 95th percentile

How doctors use BMI

BMI is not accurate enough to use as a diagnostic tool, but it can screen for potential weight problems in adults and children.

If someone has a high or low BMI, a doctor or other healthcare professional might then consider other factors, such as:

  • skinfold thickness measurements, which indicate how much fat is in the body in adults and children
  • evaluations of diet and physical activity
  • discuss any family history of cardiovascular disease and other health problems
  • recommend other appropriate health screenings

The doctor or healthcare professional can then make diet and exercise recommendations based on these results.

Health risks of extra weight

Excess weight has the following effects on the body:

  • It increases how hard the heart has to work.
  • It raises blood pressure, blood cholesterol and triglyceride levels.
  • It lowers high-density lipoprotein (HDL), or good cholesterol levels.
  • It can make diabetes and other health problems more likely.

According to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), carrying extra weight can increase the risk of the following conditions:

  • hypertension, or high blood pressure
  • dyslipidemia, which involves high LDL cholesterol, low HDL cholesterol, or high levels of triglycerides
  • type 2 diabetes
  • coronary heart disease
  • stroke
  • gallbladder disease
  • osteoarthritis
  • sleep apnea and respiratory problems
  • some cancers, including endometrial, breast and colon cancer

Carrying extra weight as a child or teenager can also pose significant health risks, both during childhood and into adulthood.

As with adult obesity, childhood obesity increases the risk of various health problems, including cardiovascular disease, diabetes, and sleep apnea.

The American Heart Association (AHA), point out that children with a high BMI also have a higher risk of:

Benefits of a healthy weight

Walking with the family helps Body Mass Index levels
Walking with family or friends can be an enjoyable way of keeping fit and preventing unwanted weight gain.

Apart from reducing the risk of the health conditions, maintaining a healthy weight offers additional benefits:

  • fewer joint and muscle pains
  • increased energy and ability to join in more activities
  • improved regulation of bodily fluids and blood pressure
  • reduced burden on the heart and circulatory system
  • improved sleep patterns

Other measures of a healthy body

BMI is a useful tool, but it cannot identify whether a person’s weight is made up of muscle or fat.

For example, an athlete with a lot of muscle tissue may have a higher BMI than a person who is not very active. But, this does not mean that the athlete is overweight or unhealthy.

In addition, cardiovascular disease and high blood pressure are more likely to occur in people who have additional fat — known as visceral fat — around their middle rather than their hips.

Other measures of body size include waist-hip ratio, waist-to-height ratio, and body composition, which measures body fat and lean body mass. These measurement systems focus more on the amount of fat a person has and its distribution around the body.

Together with BMI, these additional measures can help to assess more accurately the health risks associated with an individual’s weight.

Takeaway

Body Mass Index can be a useful screening tool for predicting certain health risks. However, people should use it with caution, as it does not take other factors — such as activity levels and body composition — into account.

For children and teens, it is important to include their age and sex when taking a BMI measurement, because their bodies continuously change as they develop.

BMI calculators and charts

BMI Calculators and Charts enable health professionals to evaluate the optimum weight of individuals. Body mass index, or BMI, is one way a person can check if their weight is healthy or not. BMI takes both height and weight into consideration.

Carrying too much or too little weight can increase a person’s risk of health problems, either now or in the future.

BMI is not the only factor that affects this risk. Other tools for assessing whether a person has a healthy weight include waist-to-hip ratio, waist-to-height ratio, and body-fat percentage.

However, BMI is a useful starting point. This page provides some tools for people to work out their BMI.

BMI calculators

These BMI calculators and charts can give an indication of whether a person’s weight may affect their risk of health problems.

We are publishing the calculators here courtesy of The Calculator Site. There are two calculation options available: Metric and imperial.

1) Metric BMI Calculators

2) Imperial BMI Calculators

BMI charts

To use the charts below, find your weight in pounds along the top and your height in feet and inches down the side. Then look across to find your BMI.

There are two charts. If a person’s weight is 200 pounds (lb) or under, they should use the first chart. If their weight is over 200 lb, they should look at the second one.

The shaded areas correspond to BMI values that indicate either a healthy weight, excess weight, or obesity.

In addition, researchers and clinicians divide obesity into three categories.

  • Class I: BMI is 30 to 34.9
  • Class II: BMI is 35 to 39.9
  • Class III: BMI is 40 and above

The charts are an adaptation of the Adult body mass index (BMI) chart. created by the University of Vermont, in the United States.


Body mass index chart: Weight from 95–245 pounds

bmi chart underweight to overweight
Adult BMI chart showing ranges “under healthy weight: BMI

Body mass index chart: Weight from 250–400 pounds

obese bmi chart
Adult BMI chart showing ranges “obese I: BMI 30–34.9,” “obese II: BMI 35–39.9” and “obese III: BMI? 40.”

These figures are only a guide. The BMI Calculators will not determine whether a person has an ideal body weight, but it can help to show if an individual’s weight is increasing their risk for disease.

A person who is very fit, for example, an Olympic athlete, may have a high BMI.

This does not necessarily mean that they are overweight. The excess weight, in this case, may be due to increased muscle mass.

BMI categories

The following table shows the standard weight status categories associated with BMI ranges for adults:

BMI Weight status
Below 18.5 Underweight
18.5–24.9 Healthy
25.0–29.9 Overweight
30.0 and above Obese

BMI of less than 18.5

A BMI of less than 18.5 indicates that you are underweight, so you may need to put on some weight. You are recommended to ask your doctor or a dietitian for advice.

BMI of 18.5–24.9

A BMI of 18.5–24.9 indicates that you are at a healthy weight for your height. By maintaining a healthy weight, you lower your risk of developing serious health problems.

BMI of 25–29.9

A BMI of 25–29.9 indicates that you are slightly overweight. You may be advised to lose some weight for health reasons. You are recommended to talk to your doctor or a dietitian for advice.

BMI of over 30

A BMI of over 30 indicates that you are heavily overweight. Your health may be at risk if you do not lose weight. You are recommended to talk to your doctor or a dietitian for advice.

Health risks

A healthy weight can help prevent a range of diseases and health conditions.

People with a BMI of 30 or more have a higher risk than others of diseases such as heart disease, type 2 diabetes, sleep apnea, high blood pressure, colorectal cancer, for example. Some of these can be life-threatening.

Having a BMI of under 18.5 can increase the risk of malnutrition, osteoporosis, anemia, and a range of problems that can result from various nutrient deficiencies. It can also be a sign of a hormonal, digestive, or other problem.

Varying cutoff points

Evidence suggests that the associations between BMI, percentage of body fat, and body fat distribution may differ across populations, due to variations in race and ethnicity.

A Brazilian study, published in 2017, looked at the correlation between BMI and body-fat percentage in 856 adult men and women.

They concluded that to predict obesity-type body-fat percentage:

  • The standard BMI threshold of 29.9 kg/m2 was appropriate for men.
  • A more suitable cutoff point for women appeared to be 24.9 kg/m2.

In 2017, Korean researchers pointed out that people in the Asia-Pacific region often have a higher risk of type 2 diabetes and cardiovascular disease at a BMI below the existing WHO cutoff point.

In Korea, they added, there is evidence that almost twice as many people have features of metabolic obesity but a normal weight compared with the U.S.

In 2010, results of a study published in The International Journal of Obesity found that Asian Americans within the healthy weight range were more likely to have symptoms of metabolic syndrome than their non-Hispanic white counterparts.

The following table, published in 2006 by the World Health Organization (WHO), shows some comparisons and cutoff points that may apply.

Doctors may use these variations when treating or advising specific people.

Classifications BMI (kg/m2)
principal cutoff points
BMI (kg/m2)
additional cutoff points
Underweight
Severe thinness
Moderate thinness 16.00–16.99 16.00–16.99
Mild thinness 17.00–18.49 17.00–18.49
Normal range 18.50–24.99 18.50–22.99
23.00–24.99
Overweight ?25.00 ?25.00
Pre-obese 25.00–29.99 25.00–27.49
27.50–29.99
Obese ?30.00 ?30.00
Obese class I 30.00–34.99 30.00–32.49
32.50–34.99
Obese class II 35.00–39.99 35.00–37.49
37.50–39.99
Obese class III ?40.00 ?40.00

Takeaway

BMI is a useful tool that gives a general idea about whether a person’s weight is healthy or not. However, it is a simple tool that does not tell the whole story about people’s individual weight and health risks.

Anyone who is concerned about their weight should speak to a doctor, who may also consider the individual’s body-fat distribution and the ratio of their waist size to their height. A health professional will also be able to offer advice to suit every individual.