Diet Composition for Maximum Fat Loss
Calories do count. But they are not the only thing that counts. The person that eats a 1500 calorie diet of tuna and green vegetables will look considerably better than the person who eats a 1500 calorie diet of soda and bacon….even if they weigh the same amount.
Diet composition is the percentage of each of the macronutrients (protein, fats, carbohydrates) that make up our diets. There are multiple opinions (and supporting research) regarding the optimal ratios for maximum fat loss. In the end, it is probably more important to focus on the type of fat (omega-3 and monounsaturated preferentially over saturated and omega-6 polyunsaturated) and carbohydrate (whole grains, fruits and vegetables over sugar and processed grains) than to obsess over macronutrient ratios.
Make no mistake, low carbohydrate diets burn fat like there is no tomorrow. In fact, low carbohydrate diets beat low fat diets when compared head to head. Excess carbohydrate also appears to be one of the primary contributors of weight gain, and may decrease leptin secretion. There also appears to be less of a metabolic slowdown while dieting with a low carb diet than a low fat diet.
On the other hand, some of the greater weight loss shown by the low carb dieters may be due to the depletion of glycogen and its associated fluids and lower caloric intake (though this could be seen as a positive for low carb dieters in that they are able to sustain at lower calories without excessive hunger issues). If you are to succeed on a low fat diet, the quality of the carbohydrates becomes extremely important. When quality carbohydrates are emphasized, the advantages of a low carb diet seem to disappear. Fiber seems to be the most important thing here, the more the better.
Eating more lean protein may make you leaner whether you choose a low fat or low carbohydrate diet. High protein dieters lose more fat than low protein dieters, though high protein diets are associated with a higher bodyweight.