Skinny genes?

Health New research has revealed that the key to both weight loss and obesity may lie in our biological make-up.

Now it seems that the reasons behind overeating are much more complex than was originally thought.

As a population we have never been more stuffed with food. An apparently limitless supply of delicacies from all over the world is ours for the taking any time we want. With the rise of all-you-can-eat buffets and portion control disappearing in a sea of fast-food outlets, obesity is a growing problem in the United Arab Emirates.

However, modern research into the condition suggests that there is more to blame than the 21st-century impulse to supersize everything. Both the rise in production of high-fat foods and the growth of the fast-food market have had an undeniable effect on the population's waistline. But consumption, it seems, may not be the sole culprit behind obesity. Research into overeating is revealing an increasing amount about the biological factors that contribute to weight gain. Last year researchers found that Caucasian people carrying two copies of a particular variant of the fat mass and obesity-associated (FTO) gene are 70 per cent more likely to be obese.

The latest study into the variant form of the gene has revealed that it probably also affects appetite. Monitoring over 3,000 children, researchers discovered that those with the variant gene were less likely to realise when they were full. Published in the Journal of Endocrinology and Metabolism in July, the results occurred regardless of age, gender and socio-economic factors. While this uncovers a further genetic cause for weight gain, how can such research curb the obesity epidemic? Professor Jane Wardle, who led the investigation, says: "This could help people. Perhaps we could help them to organise their microenvironment so that they are not around large plates of food and therefore less at risk of overeating. It could help them to be more careful.

"The work we have done may even be important in prevention of obesity. I'm not sure how the benefits could pay off, but if you can identify early on the risk of obesity there must be some way of helping." The potential advantages of investigation into this variant of the FTO gene are yet to be experienced by those who are obese. However, such studies are paving the way for methods to treat the condition.

Dr David Savage, senior research fellow at the Institute of Metabolic Science at Cambridge University, says: "The story about the FTO gene is that we've always suspected body weight is correlated to a genetic component. Many years ago studies were carried out on twins and even if one of them was in a different environment to the other they were still a similar weight. "Developing a treatment from this study is a long way off. It will be affected by our understanding of how the FTO gene works and we hope that, through understanding this, it will reveal new drug targets. However, this probably won't happen for 10 years or so."

While the variant FTO was the first clear genetic link to obesity, there are other biological factors that could be manipulated to control body weight. Two teams of researchers from Harvard Medical School have found different functions of brown and white fat cells in mammals that could lead to a weight-loss treatment. Published in the August edition of Nature, the study revealed that while brown fat cells burn fat to generate heat, the latter store extra calories consumed, which results in weight gain. Brown fat consumes energy so vigorously 50 grams of it can burn 20 per cent of person's daily calorie consumption, according to the study. In adults, white fat cells far outnumber brown.

Brown fat cells have a different function to white due to their increased number of mitochondria, which regulate cellular metabolism. White fat cells have far less mitochondria and therefore simply store fat. Savage explained: "It has always been clear that humans have brown fat in early life. Babies need it to stay warm, whereas older humans develop behaviour such as putting on warm clothes to cope with the cold without brown fat.

There is not a specific age that humans begin to lose brown fat. The mitochondria which give these cells their colour disappear in the growing process and eventually they become regular fat cells. However, a 2007 study by Stockholm University found that many adults still have some brown fat in their upper chest and neck. "Scanning technology has revealed that some people have brown fat in adulthood," says Savage. "In a study, Japanese labourers working in a cold environment were found to have more brown fat than usual. This suggests that you could develop a treatment if you were able manipulate how much brown fat a person had and therefore regulate their weight. Again, this development is a long way off, though."

Meanwhile, a year-long study published last month claimed that a chemical imbalance is the reason why some people overeat. Carried out by the University of Austin and printed in the journal Science, research found women with a smaller flow of dopamine - the hormone which rushes to the brain to signal pleasure - find food less satisfying. To compensate, the study found, these women eat more. While the findings were greeted with interest, nutritionists maintain that weight gain and obesity are solely the result of eating too much and not exercising enough. Although he agrees that this is a factor, Savage adds: "At the end of the day this research and these findings get out the message that obesity is not just a case of overeating and sloth.

"Although it is a consequence of eating more energy than you expend, there are biological processes that regulate the metabolic rate. People who are overweight are not just lazy." As well as helping people to lose excess weight or to avoid gaining it in the first place, by identifying genetic, biological and chemical links to obesity, scientists are hopeful that other advances will help with the goal of staying healthy in the long term.

A study released in August claimed that a pill can help people to keep the pounds off after a diet. An investigation carried out by the scientific firm Immorgene Concepts found that taking the dietary supplement alpha-lipoic acid after a six-month weight-loss programme can "lock in" the effects of the diet. The study, in conjunction with Liverpool University, discovered that the supplement, readily available in many countries, could trick the body into thinking it was still on a calorie-controlled regime.

However, as rats were used in trials, opinion is divided over the effect this pill would have on humans and the NHS Knowledge Service in the UK asserted that this research should be viewed as preliminary. Although the reasons for obesity, weight gain and overeating still seem to be riddles for scientists to solve, continuing research is the way to develop a treatment. Savage says: "We are trying to understand more and more the carefully defined nerve pathways that regulate appetite and metabolic rate. If we can understand what controls our drive to overeat we could identify a form of treatment."

Despite this he, like many, advises diet alteration and increasing activity until the benefits of research reach fruition: "Tiny changes over a lifetime can have a big effect. Drastic diets are all very well but it is more important to get people to change their habits in a subtle and sustainable way."