Should ‘yo-yo’ dieting mean ‘no-mo’ dieting?by Patrick O'Neil, Ph.D.Psychiatry and Behavioral Sciences Before we embark on our main topic, let’s pause to bestow a Truth in Labeling Award to the makers of Light n’ Lively yogurt. On the front of the container of Light n’ Lively’s “Free” blueberry yogurt is the following disclosure: “No fat and 6 percent more calories.” That’s right, 6 percent more calories. The added calories apparently come from the sugar added flavoring. Neither version is much of a caloric bargain: The teeny six-ounce container of the nonfat stuff provides 190 calories while the full-fat stuff offers 180 calories. Kudos to Light n’ Lively for their candor and for illustrating why simply counting fat grams won’t keep you from taking in too many calories. Sometimes, low fat or even no fat means “mo calories.” Today we offer new evidence that the common wisdom can be uncommonly unwise. A history of losing and regaining and losing and regaining, etc., is all too familiar to many weight managers. Reports in the popular press have repeatedly claimed that this pattern of weight-cycling, sometimes called “yo-yo” dieting, is self-defeating. The lore is that every time you lose weight, you lose fat, leaving you with a progressively higher body-fat percent. Further, it’s been claimed that when you diet and lose weight, your metabolic rate slows down and stays lower even if you regain. (A study from Rockefeller University, showing that people who lose weight burn fewer calories, dealt only with the still reduced people.) Most of these allegations stem from a study done years ago that measured the speed of weight loss and regain among subjects who’d previously lost and regained. However, the subjects were not overweight humans who’d had their share of ups and downs on the scales, instead, they were rats. Since then, several researchers have examined this issue with human dieters, comparing people who’ve had many cycles of loss and regain to others who’ve been more weight stable. The results have led many observers of the yo-yo dieting claims to smell a rat. These studies haven’t shown that cyclers have more fat or lower metabolic rates than non-cyclers of the same size. In most cases, they also haven’t shown cyclers to lose weight more slowly. A study presents even more compelling evidence that in the unhappy event you regain those pounds you worked so hard to lose, you’re no worse off in the body-fat or metabolic rate departments than you were originally. Researchers at the University of Pennsylvania examined twelve obese women before weight loss, then after an average loss of 42 pounds, and again a couple of years later when they’d regained just about all of their losses. (These unlucky subjects were selected from a larger study.) What made this study different is that it evaluated the same group of people before and after weight loss and after regain. Immediately after weight loss, the women’s metabolic rates dropped about 8 percent. Of course, their weight had dropped 19 percent; smaller bodies require fewer calories. After regain, the metabolic rates were right back where they started. Of the 42 pounds that the average subject lost, 34 came from fat and eight came from lean body mass (muscle). Substantial weight losses are rarely all fat. The regained pounds were the same composition as the lost pounds, the average body composition after regain was no different than before loss. From a health standpoint, it matters not only how much fat you have but where you carry it. Upper body fat (waist up) is more of a health risk than lower body fat. “Hazardous waist” is not a misspelling. One more of the common beliefs about weight cycling are that it leads to more upper body-fat. This was not true for these subjects whose waist to hip ratios were unaffected by their regain. What about the unsettling fact that many people who’ve lost weight not only gain it back but add a few more in the bargain? The Penn study indicates that this can’t be blamed on metabolism. There may be other biological factors at work that haven’t yet been identified. For now, some of the likeliest explanations for these regain bonuses offer little consolation: Discouragement that encourages overeating and under excreting, and the drift towards a higher weight that in this country often accompanies getting older. An important, yet unanswered question is this: What is the course of weight for overweight people who do nothing about their weight? Some evidence suggests that the picture here is also one of weight gain over years. It may prove to be that even short lived weight losses help one to avoid gaining as much as would be if weight were ignored. Don’t take this discussion as an advertisement for regaining the weight
you’ve lost. The point is that if you’ve had some experience with losing
and regaining, that’s no reason to give up on controlling your weight.
Hang in there!
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