The bottom line: if you’re overweight, you need to eat less. But counting calories is stressful, so the best solution would be a diet that you eat less of without thinking about it. Well, a couple of years ago nutritionists at the University of Washington described the perfect way to do this: double the amount of protein in your diet and reduce the amount of fat. You’ll eat 472 kcal less each day without even noticing it.
It’s common knowledge that a protein-rich diet is a superior slimming diet, and that a protein-rich diet suppresses appetite. What’s interesting about this study is that it tells you exactly how many fewer calories you eat if you increase the amount of protein in your diet.
Most westerners get about 15 percent of their kilocalories from proteins. By replacing as many fatty foods as possible with lean proteins, such as low-fat cheese, skimmed milk and lean meat, the researchers managed to raise that amount to 30 percent in their 19 test subjects. The amount of carbohydrates the subjects ate remained the same. The increase in the protein portion was compensated for with a decrease in the amount of fat in the diet.
At the start of the experiment the subjects ate normally [CRC1]. Then the researchers raised the amount of protein to 30 energy-percent [CRC2], but the subjects had to continue eating as much as they had in CRC1. After that the subjects could decide for themselves how much they ate for a period of 12 weeks, but they had to stick to the protein-rich diet. At the end of the period, the researchers measured how much weight the subjects had lost [CRC3].
The figure below shows that the energy intake decreased by a total of 472 kcal [triangles] and that the subjects lost about 5 kg [circles], of which 4 kg were fat. The subjects did no exercise, by the way.
In the figure above the triangles represent the feeling of fullness and the circles the feeling of hunger. The satiating effect of the protein diet seems to decline after 12 weeks, but food intake does not increase.
“A 15% increase in energy from dietary protein at constant carbohydrate intake produces a sustained decrease in ad libitum caloric intake that results in clinically significant weight loss”, the researchers conclude.
Am J Clin Nutr. 2005 Jul; 82(1): 41-8.