Exercise before or after food?
Fitness consultant Craig Wise explores this tricky question.
Exercise and food are two subjects where conflicting advice abounds. Put those two together, and it gets more confusing than ever. A big question that’s regularly thrown at me is: How should we time exercise and food with each other to get the best results?
Over the years, there has been a huge amount of research backing the theory of eat first then exercise. Unfortunately, there’s just as much that says exercise first and then eat! So which should we do? Whose research should we believe?
BREAKFAST TIME
Some people will tell you that they can’t consume anything before their early morning exercise (except maybe their coffee or smoothie). Another group says that they can’t function without fuelling their body first.
In fact, both are acceptable answers. Nobody wants to curl up with cramps because they feel like they’re exercising with a kettle-bell in their stomach, but also nobody wants to collapse like those marathon runners at the Olympics because they don’t have enough fuel left to keep going.
You can best answer the question for your particular situation by, first, looking at the goal of your activity and, second, listening to your body.
Is burning fat your main goal? Research from the University of Bath,1 while only a small study, showed that moderate exercise for less than an hour, for example a brisk walk, burned more fat when it was before eating than after. These findings have since been replicated with other small groups.
If you want to lose a little weight, this may be the way to go. Most people have enough fuel stored in their bodies for some moderate activity – about 45 to 60 minutes – when they wake up in the morning. But remember, activity in this “fasting” state is only really productive if you’re putting the effort in. If you’re doing less than you could because you’ll collapse if you go any harder, then you might still be better to wait till after breakfast.
Whether you want to eat breakfast first and then get active, or vice versa, one of the key things to remember is that when we wake up in the morning our bodies are often dehydrated – so drinking some water is vital.
LUNCHTIME AND AFTERNOON
There are people who are genuinely not morning people, and the thought of activity before or after breakfast sounds like a nightmare. If this is you, go with what your body is telling you, and do your exercise later in the day. Similar rules apply to exercise at this time as in the morning. If you’re a light lunchtime yoga enthusiast, then heading to the studio before you eat will do no harm. And as I mentioned earlier, research shows that moderate exercise before a meal is likely to burn more fat than moderate exercise afterwards. However, if you’re planning a heavy weight session at the gym, then you need to consume some protein (for muscle growth and repair) and some carbs (for fuel) at least an hour before your workout. This will ensure that your body cankeep going through the session.
AFTER DINNER
Some exciting recent research on food and exercise is particularly relevant to people with any form of diabetes. Is blood sugar control your main exercise goal? A study by the University of Otago2 looked at how the timing of exercise impacts on blood sugar levels. The study showed that brief, moderate activity after a main meal is especially beneficial for bloodsugar control. The study showed that 10 minutes of brisk walking after each main meal helped to control blood sugar levels and post-meal glucose spikes more than a single 30-minute walk once a day. These results were especially noticeable when it came to the after-dinner walks, partly because dinner is often the biggest meal of the day.
This research has since been adapted to look at other forms of exercise, such as resistance training. There, again, it was shown to work in a similar way, helping control the high blood sugars that happen after meals, especially the heavy evening meal. There are other benefits to light exercise after eating, too. For example, it moves food from the stomach to the small intestine faster. This movement releases the hormones responsible for feeling full. There may also be links with decreased levels of heartburn.
However, all post-dinner activity is not equal. Research has only shown that moderate levels of activity benefit from being soon after the meal. Vigorous exercise straight afterwards can have the reverse effect because, as the blood is drawn to the muscles to fuel the movement, it is withdrawn from the stomach, leading to a longer digestive process.
IN SUMMARY
Yes, the timing of your eating can make a difference, but exactly what you should do depends on your goals:
• Fasting before exercise is a good idea, so long as your workout is of low to moderate intensity and your goal is fat loss or weight maintenance. Just be aware of your body and its signs. If you start to feel light headed or that you’re losing energy rapidly, then stop the workout. If this happens often, think about eating before exercise.
• If you’re up for a more vigorous workout, make sure that you get some protein and carbs in beforehand – but give your body time to digest them. Don’t do the exercise straight after eating.
• If you’re looking for blood sugar control, then exercise moderately after each main meal. This is especially helpful after dinner. Don’t leap straight up from the table and rush out of the door, but do get active within an hour. That’s because, after about an hour, your blood sugar levels begin their spike, so you want to get ahead of the game.
At the end of the day, everybody is unique, and our bodies react in different ways to activity. The masses of research done have given us some guidelines, but you will need to experiment yourself to see what works best for you.