Should You Exercise on an Empty Stomach for Best Results?

I’m writing this at 35,000 feet, flying to Seoul.

My rise at 4:40 a.m. for a 7:55 a.m. flight didn’t leave me with any time to work out this morning. Then again, my pre-dawn start meant my body started burning fuel earlier than normal.

I grabbed a little oatmeal and a cup of coffee in the business lounge at Chek Lap Kok. But I’m still feeling peckish on the flight. That omelette I see heading my way on the trolley sure looks good.

My early rise probably would have been a good time to get in some exercise if I had had time, and wasn’t running for a flight. I’m all for exercise early in your day.

A friend of mine was asking me whether it’s better to work out on an empty stomach, and the answer appears to be that it is, particularly if you’re looking to burn fat.

Working out before you’ve eaten breakfast makes it easier to tap your stores of fat for energy, which is what your body turns towards when it doesn’t have easy energy from carbs.

Scientists in Belgium tortured study subjects who were healthy, active young men by cramming them full of “a truly lousy diet,” as The New York Times describes it, with 50% more fat and 30% more calories than the men had been consuming. Some then did no exercise; others had a big carb breakfast and then worked out hard; and the others worked out the same way before eating a similar breakfast afterwards. They did that for six weeks.

Those that exercised first thing gained almost no weight, despite their crappy diet. Those that “breakfasted” first gained less weight than the guys who just sat around. But they were building fat in their muscles and their bodies weren’t working right – they started resisting insulin, which turns glucose sugar into energy.

I have my doubts about this, though. I’m never hungry right after I exercise. So I wonder whether the empty-stomach crew really filled their bellies as much as those that ate first thing. And let’s not forget – they were all eating food that’s bad for your body.

It’s not a given that pre-breakfast workouts work best – as usual the scientists say more science is necessary – and there’s separate science that suggests cycling through fast and feast over the course of a month doesn’t do you any good at all.

Your performance is poor when you work out in the morning. I can only go at half pace on my workouts, and I normally cut them short. Bottom line: I exercise less.

A separate study conducted at the University of Bath in Britain took overweight and sedentary young men and got them to walk for an hour on a treadmill at a moderate pace. Before one walk, they skipped breakfast. Before the other, they had a 600-calorie meal of toast, jam, cereal, milk and orange juice two hours before their walk.

The guys used up more fat when they walked before they ate. Their genes fired up to improve insulin levels and keep their blood sugar under control. Those genes were much more active than when they had eaten.

But on the other hand, when they had already eaten breakfast, they burnt up more calories in their exercise. So if you make up for your starving workout by scarfing down more food once you get done, you’re undoing much of the good work you’ve done.

Your body isn’t very good at burning fat fast, so empty-stomach exercise is probably of a poorer quality. There’s a reason pro athletes tend to stock up on carbs before they attempt to perform.

If your goal is purely weight loss, the studies suggest empty-stomach exercise is the best way to go. If your goal is to get toned (or even build muscle) and in shape, you’d be better off fueling a decent workout, and if you’re also looking to lose weight, you simply need to exercise enough to use up all the calories you take in during the day.

Exercise in the morning leaves me energized, and I think it jump-starts your system. So I would recommend working out first thing if you can. Eat a healthy breakfast of cereal, fruit, congee or a high-protein high-carb energy bar: I think you can’t go wrong if that’s before or after you exercise.

I still think the most important element is that you exercise at all – even an evening workout works. And it’s vital to get your heart really pumping with some high-intensity exercise, particularly if you want to keep your workouts short. This elevates your metabolism. I just don’t have it in me – probably literally – to really get going without a little fuel to sustain me.

I think you’re on the right track if you “carb up” in the morning, and then taper off the amount of carbohydrates you eat throughout the day. Yet another study (sigh) shows that it’s best to have a big breakfast, a little less at lunch, and your least amount of food at supper time.

For some reason those scientists studied Seventh Day Adventists instead of the young men that the scientists tortured in the other two experiments. I’m not sure why they did that, but Adventists don’t smoke, don’t drink much, and are often vegetarian (half in the study were). So there’s that.

But this makes eminent sense to me – your meals follow your pattern of activity. The problem is that it’s hard to follow this pattern when we’re rushing out the door first thing. Doubly so if the only meal where you get to sit down and spend some family time is dinner. Eating meals last thing probably doesn’t do you any good at all – although I’m often guilty of this, having exercised in the evening and not felt hungry until late at night!

Three separate studies: taking healthy, active young men and cramming them full of fat; taking overweight sedentary young men and making them walk; and taking saints and telling them to eat at odd times.

I’m not going to throw my hands up and say “One study says this, one says the opposite” – that’s not true, and these scientists worked hard to make their studies hold up. They’ve explained the findings and their flaws.

Condensing their differing conclusions, and different results, and my own experience, and I would say:

  • Working out early in the day is best
  • Working out at all is better than nothing
  • You burn more fat on an empty stomach
  • You get a better workout with a bit of high-quality fuel
  • Eating more, early, and less later is best
  • Eating well is more important than when you do it

There you have it. I’m willing to stand corrected that pre-food exercise is the best by far; it may well be the best fat-burning strategy. But exercise is also supposed to be pleasurable, a joy. So is food, for that matter.

A sensible carb-based, protein-rich, low-fat breakfast surrounding morning exercise sounds like the way to go to me.

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