Fat burning during exercise: can ergogenics change the balance?

Phys Sportsmed. 1998 Sep;26(9):56-68. doi: 10.3810/psm.1998.09.1143.

Abstract

Endurance athletes and dieters are eager to burn more fat during exercise; athletes hope to conserve carbohydrate stores, while dieters wish to decrease fat stores. This article briefly reviews the role of fat as an energy source for physical activity, discusses how exercise intensity and duration affect fat and carbohydrate metabolism, and assesses the nutrition strategies athletes are most likely to use in attempts to promote fat burning during exercise: caffeine ingestion, L-carnitine supplements, medium-chain triglyceride supplements, and high-fat diets. Of this group, caffeine ingestion is the only strategy scientifically proven to enhance athletic performance.