I just got back from FitnessFest in Mesa, Arizona, where one of my presentations was on weight loss. It’s a hot topic, of course, given that nearly 70% of the U.S. population is overweight or obese.
Once you lose weight, you want to keep it off. There is little point to going through the exercise (pun intended) of losing weight if you’re just going to regain it. Maintaining lost weight is itself a lot of work, and most diets don’t emphasize the critical aspect of being able to maintain weight.
Just as your body adapts to every running stride you take, so, too, does it adapt to the pounds you lose. A multitude of hormones are involved in the regulation of body weight, the concentrations of which are altered after you lose weight. Many of these alterations persist for at least a year after you start to lose weight, even after you have started to gain the weight back, suggesting that the high rate of weight regain among dieters has a strong physiological basis and is not simply the result of lack of willpower or the resumption of old habits. Because most weight-loss studies are of short duration, the only reliable proof of what works for permanent weight loss comes from the people who have actually achieved permanent weight loss. And the studies that have examined those people have shown that no one diet is better than any other. Behavioral factors—monitoring weight, exercising daily—matter more.
For example, in a study by a group of scientists at the University of Colorado–Denver, the physical activity patterns of weight losers in the National Weight Control Registry were examined. Successful weight losers engaged in an average of 41.5 minutes per day (290 minutes per week) of sustained moderate-to-vigorous physical activity, while a control group of overweight individuals exercised an average of just 19.2 minutes per day (134 minutes per week) and a control group of normal-weight individuals exercised an average of 25.8 minutes per day (181 minutes per week).
In another study from the Brown University Medical School and Miriam Hospital in Providence, Rhode Island, scientists compared the amount and intensity of exercise of successful female weight losers to individuals who had never been overweight. To be in the study, the people in the weight-loss group had to have had a body mass index (BMI) of at least 25 at some point in their lives, but at the time of the study were of normal weight (with a BMI between 18.5 and 25), had lost at least 10 percent of their maximum body weight, and kept off at least 10 percent of their weight for at least 5 years. Conversely, the people in the always-normal-weight group had no history of being overweight or obese (defined as a BMI of at least 25) and had to have always had a BMI between 18.5 and 25. Their weight also had to be stable, being within 10 pounds of their weight for at least 2 years prior to the study. The scientists discovered that the weight-loss maintainers spent more total time being physically active and spent more time doing high-intensity exercise when compared to the always-normal-weight group.
What do we learn from this research? Individuals who have lost weight require more exercise to maintain their new weight and BMI than individuals who have never been overweight and who weigh the same and have a similar BMI as the previously overweight person. In other words, if you’re 200 pounds and you lose 50 pounds so that you’re now 150 pounds, you will always need more exercise to maintain your 150-pound weight than will your friend who has always been 150 pounds. But why? Why isn’t 150 pounds always 150 pounds?
Energy balance, like most of human physiology, is largely regulated by your central nervous system, which senses metabolic status from a wide range of hormonal and neural signals and controls energy intake. In other words, when you’re thin, your central nervous system “knows” you’re thin because of the feedback it gets from specific hormones, and it regulates your appetite and storage of fat accordingly. When you’re overweight, your central nervous system “knows” you’re overweight because of the different feedback it gets from specific hormones, and it regulates your appetite and storage of fat accordingly. When you’re overweight and lose weight, your central nervous system “thinks” it needs to “correct” for your weight loss and it activates multiple compensatory mechanisms (making you feel more hungry, for instance), including changes in circulating hormones and reductions in resting metabolic rate and the efficiency of your mitochondria to produce energy via aerobic metabolism.
These mechanisms all work together to encourage weight gain and return to your original weight. To be a successful weight loser and maintain your new weight, minimize the magnitude of these compensatory adaptations by losing weight relatively slowly, using small energy deficits. In other words, don’t drastically change your life all at once by eating much less than what you’re used to and running much more than what you’re used to in an attempt to lose 5 or more pounds per week. It’s hard to sustain that drastic lifestyle. Let the drastic changes happen over time, a little at a time, so that they become habits and so that your metabolism and central nervous system have time to adjust and adapt to your changing weight.
Running as a habit is very effective at keeping your weight off once you have lost it, because running steers the calories you consume away from energy storage and into energy use. People who don’t exercise are not only more likely to gain weight, it is inevitable that they will.