My friend claims that he burns more fat doing weight training than I do running on a treadmill. Surely that can’t be right?
Richard Hamilton, London

Matt Hart answers: This is an interesting one. If you exercise at low to moderate intensity, be it running, cycling or rowing, you burn mostly fat as a fuel. During high-intensity weight training the predominant fuel used will be carbohydrate rather than fat, so your friend loses this part of the argument. However, between exercise sessions a person with more lean muscle mass (your friend) will have a higher resting metabolic rate and will therefore burn more fat than you. This is because at rest we all exclusively burn fat. So, technically, you’re both right.