Protein is crucial to creating a slimmer figure. But do you know why? As you age, the body will make more insulin since the fat and muscle cells don’t respond to it properly. Insulin will promote the storage of fat, especially around the middle, and a diet that is high in protein could help to protect you from insulin resistance. A study found that obese women who followed an eight-week diet that was made up of 30% protein, 30% fat, and 40% carbs lost more fat than those who had a diet that consisted of 16% protein, 26% fat, and 55% carbs.