Our body likes to keep things in balance and there is little doubt that regulation of bodyweight occurs, albeit with varying degrees of precision! Being overweight or obese is often considered to result from the failure of homeostatic mechanisms that regulate body weight during exposure to an environment that favours overeating and or discourages physical activity. 

It is also important to emphasise that a fluctuating body weight is the general rule, even in adults who apparently maintain a stable body weight over months, years and decades, there is in reality no absolute constancy of bodyweight.  Instead, body weight tends to fluctuate or oscillate around a mean constant value, with small to large deviations from a ‘set’ or ‘preferred’ value. This is triggered by events that are seasonal and or cultural (weekends, holidays etc), psychological (stress, depression, anxiety or emotions) and pathological (ranging from minor health perturbations to more serious disease states). 

Set point theory

The set point theory;  fat cells have a form of homeostatic control over body weight, is perhaps the most plausible explanation for long-term body stores. Set point theory states that each of us has a genetically pre-programmed set weight point that our bodies would prefer to maintain under normal circumstances. A hormone called leptin which is our natural appetite suppressant  is produced in the adipocyte and is responsible for appetite and bodyweight control.  As fat cells become full they increase production of leptin which leads to a reduction in appetite.  However most people don’t respond to appetite that well but instead are susceptible to marketing, ubiquitous snacks and the social and environmental pressures that make us all eat more than we should.  Chronic overeating will lead to a situation of leptin resistance at which point, hunger is always present.  This is part of the vicious cycle of weight gain that is not fully understood.

The existence of this set point explains why most diets don't work – they are too short term in their approach to changing weight and simply lead to a temporary shrinking of the fat cell which leads to adiposity rebound. While the obese individual can fight off the impulse to eat for a time (lower levels of leptin), eventually the signal becomes too strong to ignore. The result is rebound overeating with individuals often exceeding their previous weight.

Diets don’t work

It seems that ‘get thin fast’ remedies are on every page of every magazine and there are a whole host of "quick" or "pain free fixes" on the market. On top of this there are a number of the latest fad diets and an unlimited supply of slimming snacks, drinks and even get thin gum! Slimming and diets are big business however, sadly they don't work and often there's a hefty price to pay.

"Lose ten pounds in a week!"

‘Yes but ten pounds of what?' It's only physically possible to lose one and a half to two pounds (about 1 kg) of fat in a week, even under very severe energy restriction conditions fat loss will remain slow.  One kg of fat provides 7,000 kcals which is ample for someone to survive on under starvation conditions.  When losing weight the only desirable reduction should be in fat mass (unless oedema is present) however, rapid weight loss will result in the increased loss of lean tissues such as muscle.  Added to this, there will be loses of water locked up in the glycogen that is utilised to make up for the sudden calorie deficit. This does make weight in the short term drop dramatically, leading to the belief that everything is going well and reinforcing the belief that drastically cutting food intake is the only way to lose weight. However, this cannot and will not work in the long term and invariably results in immediate weight gain when dieters go back to their original eating habits.

To learn more about nutrition, we have a 2 day Nutrition for Physical Activity course which is also included in our personal trainer courses.

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