- Getting in a workout before you eat breakfast may affect your insulin levels and help you stay healthier.
- Exercise after a few hours of fasting may also help with weight loss, researchers have found.
- A new study out of the United Kingdom focuses on how mealtimes can affect the results of a workout.
Exercising before breakfast can boost health benefits for people, including burning significantly more fat and helping them better control their blood sugar, according to a new study published this month in The Journal of Clinical Endocrinology & Metabolism by health scientists at two British universities.
In the course of the 6-week study, researchers from the universities of Bath and Birmingham studied dozens of men with overweight or obesity who were sedentary from the Bath region in England.
The study showed that those who worked out before breakfast burned twice the amount of fat than those who exercised after a morning meal.
The researchers found that those who exercised after fasting overnight had lower insulin levels during exercise.
The participants, who engaged in moderate-intensity cycling, ate their meals before 8 p.m. the evening before the exercise.
Researchers compared results from two groups — those who ate breakfast before exercise and those who ate after — with a control group of men that made no lifestyle changes.
Researchers built the study in part on growing evidence that the timing of meals can have an impact on the effectiveness of exercise.
Although working out before breakfast over 6 weeks didn’t lead to any weight loss differences, the study found it did have a positive impact on the participants’ health, because their bodies responded better to insulin.
This effect has significant long-term ramifications: It kept their blood sugar levels in check and has the potential to reduce the risk of conditions such as heart disease and diabetes.
The researchers say their data is the first to show that exercise training before eating breakfast has an impact on moderate-intensity training exercise in men with overweight or obesity.
The researchers explained that the increase in fat use is largely attributable to lower insulin levels during exercise, which means pre-breakfast exercisers end up using more of the fat from their fat tissue and within their muscles as fuel.
“The biggest takeaways from this study are that the timing of meals in relation to exercise can have a profound impact on the responses to exercise,” Javier Gonzalez, PhD, a senior lecturer in human physiology at the University of Bath and one of the study’s co-authors, said by email.
“For people looking to maximize the health benefits of exercise, performing some sessions in an overnight fasted state is likely to provide greater benefits than performing all sessions after breakfast,” he said.
Gonzalez noted that previous research has suggested a single session of exercise performed before breakfast increases fat use. But before this study, no one knew for certain whether this increase in fat use persists over a training program or a sustained period of time.
“Here we demonstrate that the increase in fat use with exercise before breakfast persists throughout six weeks of training, even as people get fitter,” Gonzalez said. “Furthermore, this translates into improvements in insulin sensitivity and adaptations in muscle associated with glucose control.”
He added that these improvements in insulin sensitivity and adaptations to muscle have the potential to reduce the risk of developing type 2 diabetes.
Todd Astorino, PhD, a professor of kinesiology at California State University San Marcos, said health scientists have known for at least 40 years that abstaining from food before exercise enhances a reliance on fat as fuel.
“So their results showing this are not novel,” he said by email. But he said what is novel is that high insulin levels were reduced with exercise training before, but not after, carbohydrate ingestion.
“This suggests that if you have a person exercising who is at risk for diabetes or has diabetes and has high blood sugar, exercise should be done in the fasted state to foster this reduction in the insulin response to a meal, which is linked to overall metabolic health status,” Astorino explained.
He called the study’s revelation groundbreaking.
Kent Hansen, an assistant professor in the department of health, exercise, and rehabilitative sciences at Winona State University in Minnesota, says the public health message here could be that you don’t have to necessarily lose body fat to become more sensitive to insulin.
“Let’s say genetics dictate that you’re a bigger person. The public health message would say that even though you don’t lose weight, you can improve your health with a method similar to this,” he said.
The study was funded by The Physiological Society, Rank Prize Funds, and Allen Foundation.
Researchers say next steps include exploring the longer-term effects of this type of exercise and looking into whether women will benefit in the same way as men.
“We performed this study in men as a first study to ensure we had a homogenous group of people,” Gonzalez said. “We are very keen to see if the responses translate to women too.”