Influence of exercise on nutritional requirements
D. R. Pendergast, K. Meksawan and A. Limprasertkul
There is no consensus on the best diet for exercise, as many variables influence it. We propose an approach that is based on the total energy expenditure of exercise and the specific macro- and micronutrients used.
There are metabolic differences between sedentary and trained persons, thus the total energy intake to prevent overfeeding of sedentary persons and underfeeding athletes is important. During submaximal sustained exercise, fat oxidation (FO) plays an important role. This role is diminished and CHO’s role increases as exercise intensity increases. At super-maximal exercise intensities, anaerobic glycolysis dominates. In the case of protein and micronutrients, specific recommendations are required.
We propose that for submaximal exercise, the balance of CHO and fat favors fat for longer exercise and CHO for shorter exercise, while always maintaining the minimal requirements of each (CHO: 40% and fat: 30%). A case for higher protein (above 15%) as well as creatine supplementation for resistance exercise has been proposed. One may also consider increasing bicarbonate intake for exercise that relies on anaerobic glycolysis, whereas there appears to be little support for antioxidant supplementation. Insuring minimal levels of substrate will prevent exercise intolerance, while increasing some components may increase exercise tolerance.
Specifically, too high energy intake results in obesity, whereas too low an intake results in exercise intolerance. High CHO and low fat intake, or the reverse, high fat and low CHO, result in exercise intolerance and fatigue during submaximal sustained exercise. Thus, the recommendation for nutrition should be at the nadir of the ‘‘U’’ for optimal results.
Very high intensity exercise (VO2max or above), CHO (55%) intake is essential; however, minimal levels of fat (30%) and protein (15%) are required. In this case, it may be helpful to ingest bicarbonate to assist with acid–base balance. For lower exercise intensities (60–80% VO2max), where fat oxidation spares glycogen, the percentage of fat and CHO can be adjusted (40 and 45%, respectively), with protein constant (15%). At still lower percentages of VO2max, the ratio may be shifted more toward fat, levels (20 and blood borne substrates become more important. For very high intensity resistance exercise, higher protein, with CHO at 55% and fat at 25%, plus creatine supplementation are important.
In addition to the energy provided for exercise from a proper nutritional plan, one has to be mindful of the health consequences that can occur from inappropriate nutritional intake. It is clear that very high levels of fat and low CHO, or very low levels of fat and high CHO, have negative effects on immune function and can lead to cardiovascular risk factors. In addition, there are essential fatty acids needed for cellular and other functions, thus requiring a minimal level of fat and micronutrient intake. Individual food choices may influence the capacity of energy delivery during exercise, and may influence cardiovascular risk factors such as blood lipoproteins and immune factors.