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Balanced Diet Best for Keeping Weight Off
Harmful Effects of Low Fat and Low Carb Diets Override Benefits
The diet dispute never ends—but the science keeps improving. Any combination of carbohydrates, protein, and fat that reduces calories below expenditures will take off pounds in the short term. Keeping it off is the problem. A clinical trial published June 27, 2012 in the Journal of the American Medical Association concluded that a diet based on healthy carbohydrates—rather that low fat or low carbohydrates—does that best.
“Only 1 in 6 overweight and obese adults report ever having maintained weight loss of at least 10% for 1 year,” the researchers wrote in introducing the study. “The long term success rates may be even lower,” they added. One explanation is loss of motivation. The will to follow a restrictive weight-loss regimen fades over time; people give up and go back to their old eating habits. An alternative explanation, and the one the researchers choose to study, is decline in energy expenditure following weight loss. Our bodies respond to calorie reduction and weight loss by slowing down and making each calorie go farther; our survival instinct also tells us to eat more.
Led by Cara B. Ebbeling, PhD, and David S. Ludwig, MD, PhD, (associate director and director of the New Balance Foundation Obesity Prevention Center in Boston), the researchers measured the drop in energy expenditure that typically follows weight loss and contributes to weight regain. They also monitored changes in specific hormones, fat levels in the blood, and other health markers. Using these determinants, they evaluated the effectiveness of three weight-loss maintenance diets containing equivalent calorie levels.
The first diet—traditionally recommended by the U.S. Government and the American Heart Association—limited fats to 20% of total calories, with 60% carbohydrates, and 20% protein. The second diet, modeled on the Atkins Diet, limited carbohydrate intake to 10% of total calories, with 60% fat and 30% protein. The last diet was low-glycemic, similar to a Mediterranean diet, with 40% carbohydrates, 40% fat, and 20% protein.
The low-glycemic diet is designed to limit blood sugar spikes after eating and, therefore, keep energy and hunger on an even keel. “The low-glycemic index diet aimed to achieve a moderate glycemic load by replacing some grain products and starchy vegetables with sources of healthy fat and low-glycemic vegetables, legumes, and fruits,” the researchers wrote. A distinguishing feature of this diet is that refined and easily digested foods are kept to a minimum. (The Atkins-type diet also had a low-glycemic load due to severe restriction of carbohydrates.)
The first step was to put all 21 participants (overweight and obese, age 18 to 40) on a “run-in” diet (45% carbs, 30% fat, and 25% protein) for three months in order to lose 10% to 15% of their bodyweight. The run-in diet was severe, designed to make participants susceptible to weight regain. A month later, the participants began randomly rotating through the three test diets, each for 4 weeks. (All meals were prepared for the participants and intake carefully monitored.)
As you’ll see, the findings require some balancing of advantages and disadvantages.
The low-fat diet had the biggest (worst) effect on energy expenditure; it also increased triglycerides (a type of blood fat) and lowered “good” HDL cholesterol. The low-carb diet, on the other hand, had the least effect on energy expenditures, burning about 300 total calories more per day than those on the low fat diet—only 100 fewer calories than at full weight before the loss. Unfortunately, the positive results came at a cost—increases in cortisol, a hormonal measure of stress, and C-reactive protein (CRP), a measure of inflammation. “Higher cortisol levels may promote adiposity, insulin resistance, and cardiovascular disease,” Ebbeling et al explained. CRP is an independent risk factor for developing heart disease.
Those on the low-glycemic diet were in the middle, with energy burn about 150 calories a day more than those on the low-fat diet. What’s more, the good news on energy expenditure (compare to the low-fat dieters) came without any negative impact on blood fats, stress, or inflammation. On balance, that made it the best of the three diets for losing weight and keeping it off.
The researchers summarized their findings: “The very low-carbohydrate diet had the most beneficial effects on energy expenditure…, but this restrictive regimen may increase cortisol excretion and CRP. The low-glycemic index diet appears to have qualitatively similar, although smaller, metabolic benefits to the very low-carbohydrate diet, possibly without the deleterious effects of physiological stress and chronic inflammation. These findings suggest that a strategy to reduce glycemic load rather than dietary fat may be advantageous for weight-loss maintenance and cardiovascular disease prevention.”
The low-glycemic diet also has the advantage of being more user-friendly.
“In addition to the benefits noted in the study, we believe that low-glycemic-index diets are easier to stick to on a day-to-day basis, compared to low-carb and low-fat diets, which many people find limiting,” Dr. Ebbeling told e! Science News. “Unlike low-fat and very-low-carbohydrate diets, the low-glycemic-index diet doesn’t eliminate entire classes of food, likely making it easier to follow and more sustainable.”
Put another way, a balanced diet is more satisfying and easier to follow over the long term.
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According to the Ebbeling-Ludwig study, continuation of the low-fat diet (high in carbohydrates) would require about an hour of additional moderate-intensity exercise each day in order to keep the weight off. The exercise requirement in addition to losing the satiety value—and health benefits—of fatty food (fish, vegetable oil, nuts, and an occasional dessert) would likely lead to regain. On the other hand, sticking with the low-carb diet would likely produce an almost irresistible craving for carbohydrates, along with an increased risk of developing heart disease and diabetes.
That leaves the more satisfying—and healthy—low-glycemic diet, that might require a little more physical activity. Most people can benefit from a little more exercise anyway. Sounds like a win-win to me.
That type of diet, much like the Mediterranean diet, along with regular exercise, has kept me lean and happy for many years.
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