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.