Food combining (also known as trophology) is a term for a nutritional approach that advocates specific combinations of foods as central to good health and weight loss (such as not mixing carbohydrate-rich foods and protein-rich foods in the same meal). One randomized controlled trial study of the efficacy of food-combining for weight loss has been reported in the peer-reviewed medical literature and found no evidence that it was any more effective than a "balanced" diet.
There are other supposed benefits of this nutritional approach. The full digestion of nutrients enabled by "food combining" is supposed to aid in prevention of certain chronic metabolic diseases. The Hay diet is one type of food combining diet.