Our struggle to lose weight is enormous. Bombarded with a stream of mixed media messages that thin will always be in, we battle to conform to society's weighty expectations of what our size and shape should be. People often lose weight, but - and here is the crux of the problem - they almost always gain it back. According to obesity experts, more than 90 per cent of dieters regain their lost weight within one to five years. So far, no diet or behavioral modification programme has improved these odds.
In the meantime, we face a barrage of information on the latest diet or diet pill, and the information is often contradictory, misleading or even dangerous. Americans spend more than $40 billion dollars a year on dieting and diet-related products. Everyone wants a quick fix, a magic pill and, as a result, is more susceptible to scams that promise tremendous weight loss in record time. Americans are ranked as one of the heaviest nations in the world and also the most obsessed about weight. Obviously, we are going about weight loss the wrong way, since, on average, we are gaining weight.
Weight maintenance is a complicated process, with biological factors and chemical pathways at work that have yet to be fully understood. There is compelling evidence that the brain receives signals from the body to regulate weight and keep it in a genetically determined range. This suggests that the decisions about what and when to eat may not be completely under a person's conscious control.
Scientists are now studying the molecular causes of appetite and satiety, and are identifying molecules that are responsible for controlling how much animals, including people, eat. One of these molecules is thought to be responsible for keeping body weight stable by controlling appetite, so that when someone eats a large meal at night they will not have much of an appetite the next morning.
Other molecules react to messages from the body that it is not fat enough, which results in an urge to eat calorie-dense foods. The fact these chemical pathways exist makes perfect sense if you consider that the brain signals all kinds of other behaviors, including keeping a balance on the amount of water a person drinks and excretes to keep a precise balance in their body.
The theory that offers the best explanation for the body's resistance to weight alteration is known as the set-point theory; where the body appears to have a set point for body fat or weight, which is inherited and rigorously defended. It's not actually a point, but rather a range of weights the body can comfortably maintain. It is believed the range varies by about 10 per cent from a midpoint. For instance, a 150-pound woman might be able to weigh 135 to 165 pounds. If, however, her weight falls below 135 pounds or increases beyond 165, her body will respond with a series of control mechanisms designed to bring the fat levels back in line. This is done by increasing or decreasing the metabolic rate so as to restore the body to a physiologically optimum weight.
A number of experiments conducted by Rudolph Leibel and his colleagues at Rockefeller University hospital in the late 1990's support this theory. Volunteers who had maintained a stable weight without effort for at least six months (an indication that their weights were in their biologically determined range) agreed to live in a metabolic ward at the hospital. During their stay, which varied from 110 days to two years, researchers controlled what they ate, making them first gain weight until they weighed 10 per cent more than their original weight and then lose until they weighed 10 per cent less. Regardless of their size and body shape, the study found they burned 1,360 calories per square meter of body surface a day. When they gained 10 per cent of their body weight, their metabolisms sped up by 15 per cent. When they ate so little that their weights fell 10 per cent below where they started, their metabolisms slowed by 15 per cent.
Earlier evidence for set-point theory comes from a study often referred to as the starvation study, which was published in 1950. Conducted by Ancel Keys and his colleagues at the University of Minnesota, the purpose was to investigate the effects of starvation on otherwise healthy young men. More than 100 men volunteered for the study as an alternative to military service; the 36 who were chosen were those with the highest levels of physical and psychological health.
For the first three months, the men ate normally while their eating patterns, personality and behavior were studied in detail. For the next six months, the men were restricted to approximately half of their former food intake and lost on average 25 per cent of their body weight. Decreases in body temperature, heart rate, respiration and BMR (basal metabolic rate) together reflected an overall slowing of the body's physiological processes during the semi-starvation phase. During the renourishment phase, which lasted three months, some of the men lost control of their appetites and ate almost continuously. It took about five months for the majority of men to return to eating normal amounts of food and about nine months for their weight and body fat percentage to return to pre-experimental levels.
The Keys study also found that restrictive dieting and weight loss had dramatic physical, psychological and social consequences. The men experienced mood swings, depression, irritability and frequent outbursts of anger and anxiety. They became withdrawn and felt socially inadequate, while sexual interests were drastically reduced. The men were preoccupied with thoughts about food to the point where concentration was impaired. They collected recipes and cookbooks and spent much of the day planning how they would eat their allotment of food (interestingly, three went on to become chefs). This study showed that many of the symptoms that might have been thought to be specific to eating disorders are actually the result of starvation.
In all likelihood, it is repeated cycles of dieting that leads to weight gain. In the Keys study all 36 men lost weight while dieting, then regained it - plus extra pounds - when allowed to eat normally. At the end of the study, they all weighed more than they did when it began and it took nine months for their weights to normalize. It's not surprising then that most dieters, who spend an average six months of the year dieting, keep getting heavier.
But what about those individuals we read about who have successfully kept the weight off over many years? Leibel claims to have met only about five of these people in all his years of research. According to Leibel, these people willingly admit they are fighting their bodies and their lower energy requirement every day. They all claim that the only element that seems to make a difference is exercise.
Of course, our environment also has an impact on this weight range and can, says Leibel, overwhelm the weight regulatory process. In an environment where you don't have to do much physical work and high-calorie food is in abundance, it is not surprising that people are sitting "above" their upper weight range. From an evolutionary standpoint, our bodies were designed to live in a world where food was not plentiful and we experienced large intervals between eating. For our species to survive, we were programmed to accept excessive amounts of body fat more easily. There is also a clear association between the proportion of body fat in women and reproductive capacity: underweight women stop menstruating, which results in them being unable to reproduce.
Doctors rarely tell someone who is aesthetically over the normal weight range that they don't need to diet. Recently, research on the health risks of being moderately overweight has been scrutinized. In the US, obesity was downgraded from the country's biggest killer after smoking to seventh place. Scientists analyzed data, which revealed that 112,000 people were killed by obesity each year, rather than the 400,000 calculated by the US Center for Disease Control in 2004. Further findings revealed that 87,000 lives were saved because people were moderately overweight (mainly older people who were less frail). According to statistics, we are healthier and living longer, despite our increasing waistlines. It is only extreme obesity that carries a severe death risk. Studies have indicated that it may be the cycles of weight loss/gain that is causing the hypertension among the obese rather than the excess weight.
Obviously further research is warranted, but what we understand now is that when you lose weight it appears to "set off a bunch of metabolic alarms".
Just as obviously, we have to be realistic when it comes to weight management. Many of us have an ideal body weight in mind that we aspire to and yet this number is remarkably arbitrary. Unfortunately, many people, unhappy with their shape, focus solely on their weight. Again, our shape is largely determined by our genes, which means that whether we are shaped like an apple, pear, or some other fruit there is little we can do to change it. Once we can accept the fact that we do not have ultimate control over our size and shape we can focus on acceptance of our bodies and work toward improving our health. It must be a process and it must be ongoing.
Sandra Comer, Ph.D. is a Psychologist in private practice in Hong Kong and specializes in Eating Disorders.