A small study from Purdue University, US, found that when participants followed a high-protein weight-loss plan ( 1.5g of protein per kilogram of body weight ) for a few weeks, they not only lost weight, they also reported betterquality sleep than those who had less dietary protein. "Dieting may leave you feeling hungry in the middle of the night.The higher protein may provide the satisfaction and blood-sugar stabilisation necessary to prevent this midnight wake-up call," explains Lyssie Lakatos, a nutritionist not involved in the study. Even if you're not trying to lose weight, a small snack with protein and carbs (like Greek yoghurt with fruit or peanut butter on wholegrain crackers) can help stabilise blood sugar and boost brain chemicals that cause sleepiness.