The Biology of Weight Regain
Cynthia Buffington, Ph.D.
How many times have you lost weight with diet or medication only to regain all of your weight plus more? Your inability to maintain weight loss with conventional weight loss therapy is one of the reasons that you decided to have bariatric surgery. With surgery, you lost massive amounts of weight and, for a period of time, were able to maintain the weight loss. However, you have now started to regain a few pounds and these additional pounds, understandably, are causing you considerable concern, especially since the amount of food that you are eating is significantly less than before your surgery.
You are probably asking yourself, “Is it possible that the surgery is no longer working?” Is there a biological reason for this weight gain or are these few extra pounds a behavioral issue? Is it possible to regain all of my weight?”
Bariatric surgery is recognized by national and worldwide health agencies, scientific organizations and medical professionals as the most effective long-term weight loss tool available for individuals with severe obesity. Nonetheless, surgery is not a ‘cure’ for obesity and, although it is unlikely that you would ever regain all of your weight following bariatric surgery, some weight regain may occur. To an extent, behavioral issues contribute to postoperative weight regain but there is also a very significant biological basis for those extra post-surgery pounds.
Various biological mechanisms have been identified as contributors to weight regain. One of these mechanisms involves defects in fat metabolism that, in comparison to someone who has never been obese, causes a greater proportion of the calories that you eat to be stored as fat. This means if during the course of the day you eat 2000 calories and your friend who has never been obese eats the same amount of calories and both of you are performing similar daily activities, more of these calories will end up around your waist or on your hips than will be the case for your friend. How does this happen?
With weight gain and obesity, there are numerous metabolic, hormonal, neurochemical, and molecular changes that promote fat accumulation. Such conditions increase body fat size by stimulating fat uptake and storage in adipose (fat) tissue, reducing the breakdown of stored fat, and promoting the conversion of sugar (from carbohydrates that you eat) to fat, making even more fat available for storage. Many of the same conditions that increase fat cell size also lead to an increase in fat cell numbers. In fact, an individual with very severe obesity may have 10 times more fat cells than someone who has never been obese.
In addition to an increased capacity for fat accumulation, obesity reduces fat utilization (fat oxidation) by various tissues, including muscle. As most of the fat burned (oxidized) by our bodies occurs in muscle, a reduction in muscle fat oxidation would increase the availability of fat for storage. Obesity, then, promotes further weight gain by decreasing fat utilization while increasing the body’s capacity to store fat.
With weight loss, your muscle’s ability to burn fat does not improve and, in fact, there are metabolic and other changes associated with weight loss that cause an even greater decline in muscle fat oxidation. In other words, your body is capable of burning even less fat after weight loss than before, making more fat available for storage and increasing your risk for weight gain. Too, the elevated numbers of fat cells associated with your formerly obese state are likely to remain high, making weight maintenance far more difficult. Fat cell size, on the other hand, is substantially reduced by weight loss. However, with weight reduction, there are changes in fat cell enzymatic activities and responsiveness to insulin that significantly increase the capacity for these cells to once again accumulate fat, particularly with the consumption of high glycemic foods (such as sugar and processed grains) that cause blood sugar and insulin levels to spike.
A decline in energy expenditure (amount of calories the body burns) with weight loss is yet another potential cause for weight regain post-surgery. This decline in energy expenditure occurs, in part, from the reduced capacity of muscle to burn fat, as discussed above, and also from a loss of lean tissue, such as muscle. Weight loss not only reduces body fat but also decreases muscle mass, reducing your body’s capacity to burn calories from either fat or carbohydrate. In order to compensate for the lowered energy expenditure that occurs post-weight loss, energy intake (calories consumed) has to be reduced, as well. If the body is not capable of burning as many calories after weight loss as before, a few extra calories ‘here and there’ would, for certain, cause a few extra pounds ‘there and here’.
Scientists have recently found that the release of toxins from the breakdown of fat with weight loss also reduces energy expenditure. Certain pesticides and other man-made pollutants, collectively known as organochlorines, cannot be metabolized by the body and are, therefore, stored in fat. With weight loss, fat is broken down, releasing these pollutants into the blood stream. Bariatric surgery increases blood organochlorine levels, one study finding a nearly 4-fold increase in these pollutants one year post-surgery. The organochlorines, in turn, decrease thyroid hormone and interfere with the body’s ability to burn fat, causing an even greater reduction in energy expenditure than can be explained by the loss of muscle and fat.
In addition to reducing the body’s capacity to burn calories, weight loss increases the desire to consume more calories. With weight loss the body ‘thinks’ it is starving. This leads to the production of specific gut hormones/factors and brain messengers that stimulate appetite and reduce your ability to feel full. The result of these biological changes in appetite regulation is hunger and a very strong and, sometimes, uncontrollable drive to eat, along with 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 messenger that stimulate appetite and changes in the production of specific hormones that promote fat accumulation.
As is apparent from the above discussion, weight regain has a strong biological basis. However, there are behavioral changes that can be made that may actually help to correct the biological conditions contributing to weight regain. These behaviors include: 1) regular moderate activity, 2) 7 to 8 hours of sleep, 3) a diet of quality protein, fruits, vegetables, nuts, whole grains, legumes, dairy, and fish or other foods high in the omega 3e essential fatty acids, 4) a diet very low in processed grains, sugar, high fructose corn syrup, trans fat, saturated fat, processed meats, 5) compliance in taking daily vitamin and minerals, and 6) the practice of relaxation and stress-release. The addition of these behaviors to your daily life, coupled with the weight loss tool(s) provided by your surgery, will not only help you to shed those extra pounds but will also help you to achieve your desire for life-long weight maintenance.
For more information and references concerning the anti-obesity effects of these behaviors, as well as the biological causes for weight gain/regain, please review the following Beyond Change article:.
April 2006 Weight Loss Maintenance: Exercise
May 2006 Weight Loss Maintenance: Dietary Problems
June 2006 Weight Loss Maintenance: Fiber Intake
July 2006 Weight Loss Maintenance: Dairy
August 2006 Weight Loss Maintenance: Omega 3 Essential Fatty Acids
September 2006 Weight Loss Maintenance: Specific Teas
October 2006 Weight Loss Maintenance: Vitamin/Mineral Repletion
November 2006 Weight Loss Maintenance: Meal Frequency
January 2007 Weight Loss Maintenance: Coping with Stress
February 2007 Weight Loss Maintenance: Overview of Steps
May 2007 The Path to Obesity
September 2007 Why am I Regaining Weight
October 2007 Preventing Weight Regain
November 2007 The Association between Obesity and Sleep Loss
December 2007 Organochlorines and Weight Gain/Regain
April 2008 A Calorie is Not a Calorie