Eating before exercise makes it harder to lose weight

April 12, 2017

Mike Francis

If you want to lose weight when you exercise, do it on an empty stomach.

A study by researchers from the University of Bath in England examined the way the body responded to exercise by people who had fasted for 12 hours compared with those who ate a normal English breakfast of cornflakes, orange juice and bread with jam.

The finding was conclusive: Those who fasted lost more adipose tissue, or fat, than those who ate.

In the somewhat opaque language of the study, “we propose that feeding is likely to blunt

long-term adaptations induced within adipose tissue in response to regular exercise.”

In other words, if you eat before working out, you’re counteracting the effects exercise will have on your fatty tissue.

Calculating the impact of exercise

The authors of the study say this is the first time researchers have examined the effect of eating on fatty tissue before exercise. They put 10 “healthy, overweight men” through a routine involving food for some, and exercise for all.

The pre-workout breakfast deserves a paragraph of its own, so you can bear it in mind during your next bed-and-breakfast trip to England: “The meal included white bread (Brace’s thick white), cornflakes (Kellogg’s cornflakes), semi-skimmed milk (Sainsbury; British semi-skimmed milk), orange juice (Sainsbury; 100% pure squeezed smooth orange juice), spread (Unilever; I Can’t Believe it’s not Butter), jam (Sainsbury; strawberry jam) and sugar (Sainsbury; British white granulated sugar).”

Researchers took blood and tissue samples before, during and after the men worked out, which was walking for 60 minutes on a treadmill.

That’s when they learned that fat tissue responds very differently to the demands of exercise if a person hasn’t eaten beforehand.

If you’d like to know more

We’ve written a lot about the benefits of exercise. See, for example:

Weekend warrior exercise counts toward longer life »
Can exercise protect young kids from depression? »
Effects of drinking alcohol can be offset with exercise »
Exercise could reduce memory loss in breast cancer survivors »
Exercise helps prevent low back pain, study says »

The U.S. Centers for Disease Control and Prevention addresses the question: “How much physical activity do I need?” with these guidelines:

If you want to maintain your weight, do 150 minutes a week of moderate-intensity aerobic activity and 75 minutes of vigorous-intensity aerobic activity, or an equivalent mix.
If you want to lose weight and keep it off, you need to do more exercise and, possibly, change your diet.

Here’s what the CDC calls moderate-intensity aerobic exercise: