Fitness junkies have long maintained that getting up early to work out or jog before breakfast is the best way to lose weight. The body feeds on the fat reserves stored overnight rather than the added calories consumed during a morning meal.
It sounds logical, right?
Sure and there’s plenty of evidence based on a 24-hour snapshot that the process works in precisely this way.
But it’s simply not true.
So-called “fasted” exercise does have an added advantage: It stimulates fat-burning genes that can reduce your weight well after the initial exercise period.
Studies have consistently demonstrated these benefits. For example, one study in the UK compared fat-burning among groups of men that went on a morning run, some before eating breakfast, others after. The fasted group burned 20% more fat. A separate study conducted in Japan found the same result.
But here’s the problem: Short-term fat burning does not necessarily translate into longer-term weight loss. Why? Because the body tends to adapt to the rate at which it burns fat and carbs. Over time, the net loss diminishes.
The few studies that have look at the issue over time – after say, several weeks of fasted exercise – have found only a marginal advantage obtained from fasted – as opposed to fed – exercise.
How much of an advantage? As little as half a pound lost, it turns out.
Those that support fed exercise make their own claims against fasted exercise. They say that it tends to burn protein as well as fat, which means it can undermine improvements to your muscle mass and gains to your overall well-being.
But these claims are probably exaggerated, too.
First, choosing fasted or fed exercise mainly comes down to personal preference. If you’re a morning person and want to get your body moving early, especially with a partner, by all means, jog or work out before breakfast.
But if you’re not, and want to exercise later in the day – even after breakfast and lunch, it’s not going to matter all that much in the long run.
But here’s what does matter: What you eat.
You can do cardio all day, 5 days a week, and it won’t matter much if you still eat too many processed foods that are high in calories, fat, salt, sugar and low in fiber, vitamins and minerals and you avoid fresh fruits and vegetables (or over-consume high-fat vegetables like potatoes).
And portion size matters, too. Over-eating, some of it due to stress-eating, is another major factor in weight gain.
Two caveats are still in order. First, it could be that fasted exercising has a greater impact on weight loss in particular areas of your body. Some research shows that abdominal fat – often a key concern to dieters – is more likely to be reduced as a result of fasted exercise.
Second, fasted eating may not help you shed the pounds overall, but it could well impact your glucose and insulin levels – and that could be quite important if you are obese and possibly diabetic, and in fact, many Americans are.
A study released just last month tracked groups of overweight and obese men that exercised before and after breakfast and compared their results to a control group that made no lifestyle changes.
The fasted exercise group increased their ability to respond to insulin and showed an increase in proteins that help regulate glucose in the bloodstream.
By contrast, those that worked out after breakfast had insulin and protein reactions on par with those of the control group.
“Our results suggest that changing the timing of when you eat in relation to when you exercise can bring about profound and positive changes to your overall health,” Dr. Javier Gonzalez of the University of Bath, who co-directed the study, told the New York Post.
So there you have it. Overall, and without altering your food intake or nutrition, there is probably only a marginal health advantage to be obtained from fasted exercise.
But depending on your weight status and your specific weight-loss needs, and your overall health status, it could still matter –perhaps quite a bit.
The only way to know for sure? Try both methods and see which one helps you the most.