Working out before breakfast may improve fat burning, insulin

October 28, 2019 in Nutrition Topics in the News, Sports Nutrition and Exercise, Weight Management

Working out before breakfast may improve fat burning, insulin

According to a new small study, researchers at the Universities of Bath and Birmingham found that by changing the timing of when you eat and exercise, people can better control their blood sugar levels.

The six-week study involved thirty men who were obese or overweight. The researchers compared results from two intervention groups (who ate breakfast before / after exercise) and a control group (who made no lifestyle changes).

Men who performed exercise before breakfast burned double the amount of fat than the group who exercised after breakfast.

They found that increased fat burning was mainly due to lower insulin levels during exercise when people have fasted overnight, which means that they use more of the fat from their fat tissue and the fat within their muscles as a fuel. The initial study involved only men, but future studies will look to translate these findings for different groups including women.

Improved insulin sensitivity tied to eating after exercise

Over the six-week trial, the scientists found that the muscles from the group who exercised before breakfast were more responsive to insulin compared to the group who exercised after breakfast, in spite of identical training sessions and matched food intake. The muscles from those who exercised before breakfast also showed greater increases in key proteins, specifically those involved in transporting glucose from the bloodstream to the muscles.

Note, there were not any differences for weight loss between groups over six weeks.

Still, the lead research concluded that the results suggest that changing the timing of when you eat in relation to when you exercise may bring about positive changes to overall health.

The group who exercised before breakfast increased their ability to respond to insulin, which is intriguing given that both exercise groups lost a similar amount of weight and both gained a similar amount of fitness. The only difference was the timing of the food intake.


There are limitations, as always. This study was very small involving at most 30 participants, all of them men. It’s possible that, due to hormonal differences, the results may not apply to women.

The research looked at the effect of aerobic exercise (cycling) on fat burning; it doesn’t apply to strength training for building muscle strength.

Let’s not forget, too, that losing body depends largely on your daily calorie intake.  Overeating later in the day will presumably wipe out the fat-burning benefits that come from exercising before eating breakfast.

Reasons to eat before morning exercise

Exercising on an empty stomach doesn’t work for everyone. Forgoing breakfast, even a small pre-workout snack, won’t improve your performance. Something to consider if you’re training for a triathlon or half or full marathon.

During moderate to intense exercise, most of your muscle fuel comes from carbohydrates in your bloodstream (glucose) and those stored in your muscles (glycogen). Without incoming carbohydrates from breakfast, you’ll tap into muscle glycogen sooner causing early fatigue.

Working out on an empty stomach may even hinder athletic ability. A grumbling, acidic stomach can distract from the physical task at hand. And for some, exercising without fuel in the belly can be psychologically discomforting (i.e. do I have enough energy to finish my run?).

Bottom line: Whether you’re better off eating breakfast before or after your early morning workout comes down to what works for you.

Source: The Journal of Clinical Endocrinology & Metabolism, October 19, 2019.

All research on this web site is the property of Leslie Beck Nutrition Consulting Inc. and is protected by copyright. Keep in mind that research on these matters continues daily and is subject to change. The information presented is not intended as a substitute for medical treatment. It is intended to provide ongoing support of your healthy lifestyle practices.