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16 March 2005
New Study Examines How Low-Carb Diets Work 
A new study, examining the effects of a low-carbohydrate diet on appetite, blood glucose and insulin resistance appears in the current issue of Annals of Internal Medicine. The results showed participants lost an average of 3.6 pounds, voluntarily reduced their calorie intake from 3,111 calories/day to 2,164 calories/day, and did not eat more of the readily available fat and protein to make up for the lost carbohydrate calories. During the first week of the study, participants, who were obese and had mild type 2 diabetes, ate a regular diet in which they could eat anything in any quantity. They ate about 3,000 calories and 300 grams of carbohydrates per day and did not achieve any weight loss. For the following two weeks, when restricted to only 20 grams of carbohydrates per day, the participants voluntarily ate about 1,000 fewer calories per day. The participants' blood sugar improved on the low-carb diet, with better insulin sensitivity and lower blood triglycerides and cholesterol levels. "We proved that people lose weight on the Atkins diet because they eat less (consume fewer calories), not because they get bored with the diet or lose body water or because the carbohydrate calories are treated differently by the body than fat or protein calories," said Guenther Boden at Temple University School of Medicine. "All the weight loss was in fat," said Boden, who was the lead author of the study. "We weighed and measured every calorie that participants ate and every calorie they spent. We knew what went in and what went out. On the very low-fat diet, participants spontaneously reduced their calories by about 1,000 per day. One gram of fat equals 9 calories, so, doing the math, you can determine how much fat will be lost by cutting 1,000 calories." Boden believes that the carbohydrates actually stimulated the patients' big appetites during the normal-diet week. "Participants went from an excessive caloric intake to a normal caloric intake for their height and weight when we reduced their carbohydrates. This indicates to me that it was the carbohydrates that stimulated the excessive appetite," Boden said. "You don't have to cut carbs as drastically as participants did. If you cut carbs modestly, you cut calories, and you'll lose weight. The message is: Calories count. If you want to lose weight, you have to decrease your food intake or increase your physical activity. It helps to know that carbohydrates make it more difficult to reduce food intake. So cutting the carbohydrates, at least to some extent, will help keep down the caloric intake. With fewer carbohydrates, you're going to eat fewer total calories a day."
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