A common question..
A common question in the health and fitness industry is whether you should or shouldn’t exercise on an empty stomach. For many people, it’s a preference thing… eating before a workout may make people feel nauseous or vice versa. Depending on your goals and the type of training you’re doing, i.e., endurance running or HIIT will influence this decision. In addition to this, certain chronic health conditions will also influence whether you should or shouldn’t eat before exercise and what type of food you should be eating. This question can be answered in a variety of different ways depending on the above variables.
A review paper published in 2018 by Wallis & Gonzalez examined the current evidence surrounding the impact of undertaking aerobic exercise in the overnight-fasted state vs the fed state in the context of optimising the health benefits of regular physical activity.
As mentioned before the information differs for different chronic health populations, with medications and biological factors playing a role. Eating meals containing carbohydrates are known to increase blood glucose and insulin concentrations. When this is followed by exercise, glucose uptake into skeletal muscle is enhanced, leading to a lower effect on blood glucose.
This has been argued to be of particular importance in diabetes. The commencement of exercise 30–90 min post-prandial (after eating) is suggested to be optimal in accelerating meal-derived glucose removal, thus avoiding hyperglycemia and minimising the risk of post-exercise hypoglycaemia. So, in the case of diabetics, eating before training is recommended.
When comparing this population to endurance athletes, the information differs. A recent review completed by Rothschild et al. in 2020: What Should I Eat before Exercise? Pre-Exercise Nutrition and the Response to Endurance Exercise: Current Perspective and Future Directions. Highlighted that performance is improved following pre-exercise carbohydrate (30 mins prior) ingestion for longer but not shorter duration exercise
However, for the general population, the research is clear; training in a fasted state improves the ability to tap into fat stores sooner and burn a higher percentage of fat during training sessions. Sports dietitians Australia give the option of adding a small snack in the 1-2 hours before exercise for a final top-up of fuel stores. If you want more specific dietary advice on what to eat before training, please consult a dietitian.