There is little doubt that weight regain is, in part, behavioral in origin. A return to old behaviors, such as eating in response to stress, consuming foods high in sugar, fat or processed grains, failing to get enough exercise or to eat sufficient amounts of the ‘obesity prevention foods’ (fiber, calcium containing foods, and those high in omega) can most assuredly contribute to weight regain. However, physical factors associated with previous obesity, as well as weight loss, also play a very significant role in the inability of the majority of individuals who have lost weight to maintain such over time. What are these physical factors that adversely affect long-term weight loss success?
Obesity results in changes in adipose tissue (fat) metabolism, increasing the capacity for fat storage and reducing the breakdown of fat at times that the body needs fat for fuel, such as during exercise or when hungry or under stress. Weight gain also reduces the ability of muscle and certain other tissues to utilize (oxidize) fat, making more fat available to be taken up into adipose tissue and stored. Weight loss, unfortunately, does not reverse defects in the ability of muscle to utilize fat and, in fact, may even worsen such defects. Since muscle comprises a significantly large portion of the body and, under normal circumstances, utilizes large amounts of fat, a defect in the capacity for fat utilization by muscle would substantially increase the post-obese person’s chances for weight regain.
Obesity, in addition to increasing fat storage capacity and reducing fat utilization, increases the capacity for fat accumulation by increasing fat cell numbers. Serious obesity is associated with high numbers of fat cells, and studies have found that the greater number of fat cells an individual has, the more difficult it is for them to control their body size. A greater number of fat cells in previously obese persons, then, would increase the risk for weight regain.
Obesity also increases levels of certain messengers in the body known as endocannabinoids (pronounced en doe can nab i no ids). These messengers can contribute to further weight gain because they stimulate appetite, cause you to crave certain foods, increase the storage of fat into your fat storage depots, and stimulate the production of fat by the liver. Evidence suggests that with diet-induced weight loss, the elevated levels of these messengers may not decline, thereby, increasing the risk for weight regain.
Weight loss is also associated with changes in your body that increase you risk for weight regain. With weight loss, your body not only loses fat tissue but also loses muscle and other lean tissue. A loss of muscle would increase your risk for weight gain by decreasing fat utilization and by causing an overall reduction in resting energy expenditure or, in other words, a reduction in the number of calories your body is capable of burning while at rest. As resting energy expenditure accounts for approximately 70% of all the calories your body burns in a day, a lowered resting energy expenditure would substantially increase your risk for weight regain.
With weight loss, a hormone that is known as leptin, which is produced by your body fat, declines to very low levels. This hormone ordinarily acts to stimulate energy expenditure (calories burned) and to reduce appetite. The reduction in appetite results from the ability of this hormone to reduce production of certain brain messengers that, otherwise, cause you to eat more food. With weight loss and a decline in leptin, the body ‘thinks’ it is starving and, in response, the brain produces a number of appetite-promoting messengers and reduces production of those messengers that would reduce appetite and cause feelings of fullness. The result of these changes, then, would be a very strong and, sometimes, uncontrollable drive to eat.
A hormone produced by the stomach may further increase the drive to eat with weight loss. This hormone, called ghrelin, stimulates appetite and food intake. Ghrelin levels increase when the stomach is empty and there is also a substantial increase in production of ghrelin when dieting. This rise in ghrelin, is another reason for potential weight regain.
Unresolved and pre-existing psychological issues may also cause physical changes that contribute to weight regain. Most of us during the weight loss phase of any obesity regimen go through what is called a ‘pink cloud’ period when the excitement and self-esteem derived from the weight loss, along with the compliments of others, overshadow any existing psychological stressors. Often, too, we believe that with weight loss all of our problems will resolve. With the realization that those emotional problems that existed pre-diet remain, we often become anxious and depressed which, in turn, cause changes in the production of certain brain messengers that stimulate appetite and changes in the production of specific hormones that promote fat accumulation.
As is apparent from the above discussion, weight regain is a far cry from being a matter of willpower and is even much more than a return to previous weight-promoting behaviors. Rather, with weight loss there are numerous metabolic, neurochemical and hormonal changes that cause a nearly overwhelming and irresistible physical drive toward weight gain. For all of these reasons, weight regain following diet or anti-obesity meds or even behavioral therapy, is generally the ‘rule’ rather than the ‘exception’.