Are All Calories Created Equal?
The traditional calories-weight loss dogma gets turned on its head.
By Jack Challem
Conventional wisdom argues that a calorie is a calorie, whether it comes from an ice cream cone or a tossed salad. Of course, there's a huge difference in the nutritional value of these foods. Ice cream is mostly sugar and fat calories, whereas the salad is a trove of vitamins, minerals, antioxidants, and fiber calories. (Weight-loss-focused folks will be quicker to note that one of these certainly has a lot more calories than the other.)
The difference in these foods' calories goes deeper, however, according to research by Eugene J. Fine, M.D., and Richard D. Feinman, Ph.D., of the State University of New York Downstate Medical Center in Brooklyn. Calories are calories, weight-loss gurus tell us, and to lose weight you need to "eat less, exercise more." Right? Maybe not.
Against the Grain
Fine and Feinman have built a case that calories are not always equal, that some types of calories are more likely than others to be converted to fat. Their thinking is controversial because it goes against the grain of what most doctors and dietitians have been taught and preached to their patients. Calories, of course, are units of energy. The traditional view is based on the first law of thermodynamics — the "energy in, energy out" idea. This law supports the going belief that there is only one way to lose weight: consume fewer calories than you burn.
Here's the twist. Fine and Feinman have pointed out that the second law of thermodynamics comes into play in people. This law recognizes that there is always something in energy systems that somehow gums up the works. Applied to the calorie equation, some people's bodies will respond differently (metabolism-wise) to 500 calories of sugar than they will to 500 calories of protein. Obviously, this idea has enormous significance for people whose goal is weight loss.
It's in the Insulin
Our bodies' responses are influenced by insulin, a potent hormone. The body secretes insulin (or a person takes insulin) to move glucose from the bloodstream into cells, where it's either burned for energy or stored as fat. Sugary foods and other processed carbohydrates — think breads, chips, pretzels, white rice and pastas — can trigger a sharp spike in blood glucose levels. That spike is followed by a big jump in insulin (or a big dose of insulin). This is especially true in people with prediabetes and type 2 diabetes, who tend to have high insulin levels. Too much insulin secretion leads to insulin resistance.
Research tells us that excess insulin also sets the stage for inflammation, has been linked to breast cancer risk, and promotes the accumulation of belly fat. This fat-promoting effect is insulin is well known. In fact, people typically gain weight after they start insulin injections. If all calories were equal, weight loss would be equal on strictly followed low-calorie diets. But such diets, while usually low in fat, tend to be high in carbohydrates — the very foods that increase insulin secretion. And this effect is even more undesirable in the context of something we know about being overweight: According to a study by scientists at the University of Munich (Erdmann et al., 2008), just 10 extra pounds can alter normal insulin function and set the stage for prediabetes and type 2 diabetes. So if you want to lose weight, how should you compose your calories?
Weight Loss Lessons
Fine and Feinman contend that controlling insulin secretion is the key to losing weight. And findings published in the May 16, 2007, Journal of the American Medical Association backs them up: Researchers from Children's Hospital Boston reported that people with elevated insulin levels were more likely to lose weight on a higher protein, lower carb diet, instead of a traditional low-calorie and high-carb diet. The reason? Fish, chicken, and other quality protein sources barely increase insulin levels. The researchers conclude that the variability in how people lose weight may be partially due to differences in insulin response. And they say that, among people with compromised insulin function, low-glycemic eating may be the best way to achieve weight loss. Regardless of insulin function, they say, eating this way has beneficial effects on cholesterol.
None of this means you have to eat a super high-protein diet. Eating lean meat, chicken, and fish, along with high-fiber, nonstarchy vegetables (almost anything except potatoes and corn) helps control both glucose and insulin levels. And may just be the best ticket to weight control, too.
1. - Feinman RD, Fine EJ. 2004. "A calorie is a calorie" violates the second law of thermodynamics. Nutrition Journal 3:9-13.
2. - Feinman RD, Fine EJ. 2007. Nonequilibrium thermodynamics and energy efficiency in weight loss diets. Theoretical Biology and Medical Modelling 4:27.
3. - Daly A. 2007. Use of insulin and weight gain: optimizing diabetes nutrition therapy. Journal of the American Dietetic Association 107:1386-1393.
4. - Ebbeling CB, Leidig MM, Feldman HA, et al. 2007. Effects of a low-glycemic load vs low-fat diet in obese young adults: a randomized trial. JAMA 297:2092-2102.
5. - Pichard C, Plu-Bureau G, Neves-E Castro M, Gompel A. 2008. Insulin resistance, obesity and breast cancer risk. Maturitas. 60(1):19-30. Epub 2008 May 16.
6. - Tilg H, Moschen AR. 2008. Inflammatory mechanisms in the regulation of insulin resistance. Mol Med. 14(3-4):222-31.
7. - Erdmann J, Kallabis B, Oppel U, et al. 2008. Development of hyperinsulinemia and insulin resistance during the early stage of weight gain. American Journal of Physiology, Endocrinology, and Metabolism. 294:E568-E575.
Reviewed by Susan Weiner, RD, MS, CDE, CDN. 4/11
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