The Truths and Myths of Weight Loss

As discussed in chapter 2, metabolic studies show a persistent decline in the metabolic rate that characterizes the reduced obese.  Many studies show that the resting metabolic rate (RMR) decreases with diet induced weight loss by 15 to 30% below those at the same weight who have not loss (see figure 2.5).  Although the drop in metabolism takes up to weeks to maximize, this reduced metabolic state can persist for up to 6 years, making for a  predisposition back to obesity. Even though the post-obese individual can attain a body composition similar to lean individuals  both in fat and lean content, the reduced metabolic state remains after weight loss. Furthermore, the reduced RMR can not be explained away as a loss of lean tissue (muscle) and  this lowered metabolic state is not altered by exercise. As discussed in appendix III, there is no satisfactory scientific evidence that shows a prolonged increase in metabolic rate following intermittent exercise. Taken together the differences in the metabolic rates between the reduced-obese and always lean individuals are not related to changes in body composition or exercise , but seem to arise from differences in the efficiency of  energy  utilization in that the reduced individual requires less energy to function at the same weight as one who has never lost weight. The reason for this paradox still remains unexplained today.

               These reduced-obese subjects, even when still overweight, require 15 to 30% fewer calories to maintain their new weight than subjects at that same weight who have not lost weight (control subjects).  This appears to be a combination of not only a reduced metabolic rate, reduced work of movement at a lower body weight, reduced thermic effect of food (as fewer calories are eaten), but also, other energy regulatory homeostatic factors not fully understood at this time.  Although this reduced metabolic state is important, other issues have their impact on regain. Over the past 14 years, I have observed a wide variability in the amount of weight  regained  from as little as 5 pounds to as much as 100 pounds. This would suggest that  other exogenous factors contribute to weight  regain other than the body  attempting to re-establish   its previous body composition and metabolic rate. Because of the wide variability of weight regain, these factors most likely involve  not only poor adherence to physical activity, but  re-emergence of bad eating habits with excess food intake having  their impact on regaining.

            The National Weight Control Registry( NWCR)  collects data on individuals that have  maintained a 30 pound weight loss for at least a year, but on average have maintained  a 66 pound  weight loss for 5.1 years.  The key principles for maintenance of their weight loss were a combination of both increased physical activity and a low calorie diet. On average the diet closely resembles the  moderate- fat, balanced nutrient reduction diet promoted  by most health organizations for weight loss totaling around 1490 calories/day.  This is considerably less than the 2500 calories per day eaten by the average US adult. Therefore, they are maintaining their weight on considerable lower calories than those who have not lost. Their physical activity is  comparable to about 1 hour  of moderate intensity, such as a brisk walk, per day. This is much higher than the Surgeon General’s recommendations for the average adult  of 30 minutes of moderate intensity activity at least 4 days/week. Among those individuals who regained their weight, there was a decrease in physical activity and dietary restraint, particularly loss of disinhibition (loss of control while eating, or binging).  Those who have maintained their new weight for 2-5 years had a significant decrease in their risk of regaining. This underscores the importance of long term behavioral changes in diet and exercise that are needed to maintain weight loss.