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Weight-loss surgery – it’s not all about pounds and ounces

18 Jun, 2013

bariatric surgery ResearchBlogging.org

Would you donate a sample of butt fat for research? If asked, I would probably say no to letting someone take a chunk out of my ‘junk’. Fortunately for researchers at the Wellcome Trust Clinical Research Facility in Manchester, 22 people allowed them to do exactly that in order to investigate the effects of bariatric surgery (also known as weight-loss surgery).

There are a variety of surgical weight-loss options: the two most common are gastric banding and gastric bypass. A gastric band closes off part of the stomach, reducing the space available to receive food, while in a gastric bypass operation, the digestive system is rerouted to avoid most of stomach entirely. Within a couple of years, patients who keep to the accompanying diet and exercise plans can lose up to a third of their excess weight.

The Manchester team were interested in the shorter-term effects of these operations. They asked patients undergoing assessment for the surgery if they would be willing to donate a sample form their buttocks for research. After talking about it, patients were given reading material and contact numbers. Follow-up calls identified participants who then attended the research facility.

This is where the butt fat comes in, or rather, out.

First, anaesthetic was applied to a small area of the buttock. Once numb, an olive-sized sample of skin and fat was removed with a scalpel. Each sample was processed immediately into three sections, each destined for a different experiment. The hole was then stitched closed. In this way, a section of fat was removed from the buttocks of 15 obese patients before and after weight-loss surgery.

It’s easy enough to understand why people undergoing surgery would be willing to help out with the study, not least because they would get to see the wider effects of the surgery. But any good study needs a control group for a comparison – so how do you convince lean, healthy volunteers to donate a lump of their backside? The answer: ask the relatives. Seven relatives of patients due to have surgery agreed to take part.

Fat lot of good

Fat is not dead weight. It has a role in cushioning and insulating the body, and is a long-term energy store. Increasingly, it is also recognised for the role it plays in the release and regulation of hormones. The fat that surrounds blood vessels produces a whole host of chemicals, including nitric oxide and hydrogen sulphide, which stimulate vessels to dilate and thus help blood to flow.

However, in obese people the fat cells do not receive enough oxygen which can cause them die. This in turn stimulates an immune response.  Decreased amounts of oxygen and increased inflammation in the fat means that a smaller amount of the chemical dilators are produced. As a result, the blood vessels stiffen and lose their ability to relax and dilate, reducing their ability to respond to changes in requirements for oxygen-rich blood. This is called small artery disease, which is a common symptom of obesity and can cause high blood pressure and chest pain.

The Manchester researchers wanted to know whether bariatric surgery helped to restore the healthy functions of fat. They isolated the small arteries in the donated fat samples and subjected them to a battery of tests to investigate their ability to contract and relax. Before surgery the vessels’ functions were impaired, as expected. But just six months later, the responses were similar to those of arteries taken from the lean, healthy volunteers. This is mostly likely due to decreased inflammation in the fat resulting in an increased availability of nitric oxide which stimulates the vessels to relax.

Reducing surgery

Six months after surgery, the patients were still obese although all had lost weight. But they already showed significant decreases in blood pressure and waist circumference, both of which are linked to heart disease. The researchers also recorded lower amounts of insulin and glucose circulating in the blood, high levels of which are associated with obesity-related type 2 diabetes. It is remarkable that all of these improvements were seen despite the fact that patients were still clinically obese.

Dr Reza Aghamohammadzadeh, lead author on the paper, told me the research suggests that it might be possible to treat some of the problems associated with obesity, such as high blood pressure and heart disease, while patients are still overweight and without resorting to surgery. There are risks associated with all surgical procedures and these increase when the patient is overweight. More solutions that avoid surgery can only be a good thing.

Aghamohammadzadeh, R., Greenstein, A., Yadav, R., Jeziorska, M., Hama, S., Soltani, F., Pemberton, P., Ammori, B., Malik, R., Soran, H., & Heagerty, A. (2013). The Effects of Bariatric Surgery on Human Small Artery Function: Evidence for Reduction in Perivascular Adipocyte Inflammation, and the Restoration of Normal Anticontractile Activity Despite Persistent Obesity Journal of the American College of Cardiology DOI: 10.1016/j.jacc.2013.04.027

One Comment leave one →
  1. David permalink
    22 Nov, 2015 5:34 pm

    I never knew fat was so important to our bodies suppose its just excess fat we have to worry about

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