Different studies produce conflicting results on the question of which diet is best for weight loss. A recent study that looked insulin response to sugar consumption found that for people whose bodies produce more insulin in response to an oral glucose tolerance test the best diet is one that lowers glycemic index.
Overweight individuals who secrete insulin at a higher level may experience greater weight loss by selecting a low-glycemic load diet, compared to a low-fat diet, according to a study in the May 16 issue of JAMA. The researchers also found a low-glycemic load diet to have beneficial effects on HDL cholesterol and triglyceride concentrations.
"With prevalence approaching one-third of the population, obesity is among the most important medical problems in the United States and identification of effective dietary treatment has become a major public health priority. Three popular diets—low fat, low carbohydrate, and low glycemic load—have recently received much attention. However, clinical trials have produced inconsistent findings, with some suggesting that one diet is superior for weight loss and others indicating no difference between diets," the authors write. They add that one explanation for the inconsistent findings could relate to the inherent physiological differences among study participants. "One physiological mechanism that might relate weight loss to dietary composition is individual differences in insulin secretion."
A low glycemic index diet is one which contains carbohydrates in forms that break down slowly in the intestine.
A low glycemic index diet works best for people whose bodies secrete more insulin in response to consuming glucose.
The researchers found that change in body weight and body fat percentage did not differ between the diet groups overall. However, for those with insulin concentration at 30 minutes above the median (midpoint), the low–glycemic load diet produced a greater decrease in weight (12.8 lbs. vs. 2.6 lbs.) and body fat percentage (–2.6 percent vs. –0.9 percent) than the low-fat diet at 18 months. There were no significant differences in these end points between diet groups for those with insulin concentration at 30 minutes below the median level. Among all the participants in the study, high-density lipoprotein cholesterol (the "good" cholesterol) and triglyceride concentrations improved more on the low–glycemic load diet, whereas low-density lipoprotein cholesterol (the "bad" cholesterol) concentration improved more on the low-fat diet.
"The main finding of our study is that a simple measure of insulin secretion predicted weight and body fat loss on low–glycemic load and low-fat diets," the authors write. "For obese individuals with high insulin concentration at 30 minutes during an oral glucose tolerance test, a low–glycemic load diet may promote more weight and body fat loss than a low-fat diet. Regardless of insulin secretion, a low–glycemic load diet has beneficial effects on concentrations of HDL cholesterol and triglycerides but not on LDL cholesterol. Additional research is needed to examine these effects in other populations and to explore the mechanistic basis for the observed diet-phenotype interaction."
The big insulin response could cause more weight gain by a couple of mechanisms. First off, the greater amount of insulin causes the sugar to get cleared from the blood more rapidly. Therefore blood sugar drops and the more rapid return to a state of lower blood pressure probably brings with it hunger pangs. Second, some of the sugar that gets moved out of the blood gets converted into fat for storage. If the sugar came into the blood and exited the blood more slowly the body could probably burn more of it before it gets converted to fat.
A diet that does not much stimulate the islets of Langerhans. on your pancreas to pump out a lot of insulin in response to what you eat is probably a better diet regardless of whether you are trying to lose weight. Big blood sugar spikes cause sugar to bind in places harmful to your health and that accelerates aging. That is why diabetics have much shorter life expectancies.
If you want to lower the glycemic index of your diet then choose among foods that have low glycemic index. Here is the glycemic index for hundreds of foods. Also see David Mendosa's satiety index for foods.
Here is the research paper: Effects of a Low–Glycemic Load vs Low-Fat Diet in Obese Young Adults.
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