Do You Burn More Calories Working Out Before or After a Meal?

Should you eat before or after you work out? If you have a sensitive stomach, the answer may come down to which meal timing your innards prefer. But in most cases, studies indicate that eating earlier in the day leads to more fat loss.

Unfortunately, the vast majority of studies regarding meal timing are about sports performance — particularly at the elite level. However, there are a few studies on meal timing specific to weight loss that offer more helpful information.

One of the most helpful reports is a synopsis of "The Big Breakfast Study," published in a June 2018 issue of Nutrition Bulletin, which summarizes the body of knowledge regarding meal timing and weight loss to date. Although findings from the Big Breakfast Study itself are not available, the authors note that eating more of your calories in the morning than in the evening has been shown to improve weight loss, because your body uses the energy more efficiently earlier in the day — even though the mechanism behind this is poorly understood.

Hopefully, once complete, the study will shed more light on the relationship between meal timing and energy expenditure — another way of saying calories burned. But, based purely on the body of evidence leading up to the study, if you have time to eat before your morning workouts, you may find yourself burning more calories overall during the day.

In another interesting but small study involving a group of 24 active women, published in a July 2015 issue of Nutrients, researchers found that if the women ate breakfast before they worked out they felt more relaxed before lunch. The early meal also helped with their appetite control, which in turn could help reduce overall calorie intake and lead to faster weight loss. On the downside, the early breakfast also seemed to diminish the efficacy of the subjects' working memory around mid-afternoon and contributed to more mental fatigue and tension later in the day.

In an April 2013 issue of London's International Journal of Obesity, researchers related a similar finding during a 20-week study of 420 individuals: Even when the other factors they measured — including calorie intake, dietary composition, estimated energy expenditure, appetite hormones and sleep duration — were similar, people who tended to eat lunch later in the day lost less weight overall, and at a slower rate, than people who ate earlier.

Read More: Lose Weight With These 13 Easy Breakfasts

Not all digestive systems are created equal, and your body has its own unique response to exercise stimuli, based on a number of factors from your hormone levels to body composition, overall health, and activity levels both past and present.

If you want to take the "glass half-full" approach to the dearth of solid evidence about meal timing for a great calorie burn, you can look at it as free license to experiment and find what works best for you. Even if you can't really gauge your own calorie burns, you can track your energy levels depending on your meal practices, and how hard and how long you were able to work out.

If you do eat before your workouts, don't do it immediately before sweat time; having a big meal in your stomach during a tough workout is a great recipe for unpleasant symptoms like nausea and cramping. Instead, take some good advice from the Mayo Clinic and finish eating at least an hour before your workout. This helps fuel your body for a longer, more challenging workout that burns more calories.

In the same vein, if you're trying to decide whether to eat before or after a morning workout, your daily schedule might make up your mind for you. Sleep plays an important — if not well-understood — role in weight loss too. Given that you need a gap between eating a substantial meal and working out, if morning time is at a premium you may have no choice but to eat after you work out.

Read More: 10 Healthy Make-Ahead Meals

If you're participating in extended bouts of high-intensity exercise, the answer to "Should I eat before or after I work out?" is "Yes, both." For example, the Mayo Clinic recommends that distance runners eat a low-fat meal (so it's easy to digest) three to four hours before a long training run or competition or, if that's not feasible, a snack an hour or two before your workout. After your workout, a snack rich in carbohydrates and protein will help your body recover.

They also note that for long, intense workouts you should eat during your workout too. For more detail, consider the position stand released in a 2017 issue of the International Society of Sports Medicine's own publication, the Journal of the International Society of Sports Nutrition. Here, the ISSN notes that if your workout is more than 70 percent of your VO2max (one way of measuring workout intensity) and lasts for more than 60 minutes, you should eat 30 to 60 grams of carbohydrates per hour, spaced out during the workout time.

The ISSN also emphasizes the importance of getting adequate protein, noting that if you're working on building muscle, eating protein within two hours after your workout "stimulates robust increases in [muscle protein synthesis]." That consideration aside, the ISSN explains that spacing your protein intake throughout the day works well. They currently don't have a recommendation for fat intake timing.

Although eating before and after an intense workout can help fuel your body to perform and then recover, that doesn't mean you should snack constantly. Although eating small, frequent snacks is a common recommendation for weight loss, several studies cast doubt on the wisdom of that.

For example, a study published in the February 2013 issue of Obesity followed a small pool of 15 subjects who were evaluated while eating three meals a day or six meals a day. Subjects had the same overall energy expenditure and fat oxidation while on both meal plans, and they reported no difference in fullness. But the subjects who ate six meals a day reported greater hunger and more desire to eat, which would seem to contradict the common advice to eat smaller, more frequent meals to help control your appetite.

A much larger study, published in a September 2017 issue of The Journal of Nutrition, followed a cohort of more than 50,000 adults and yielded similar results, finding that eating one to two meals per day yielded a reduction in body mass index (BMI) over eating more than three meals per day, and that snacking between meals was also associated with a relative increase in BMI. They also found that eating breakfast (as opposed to skipping it) helped to decrease BMI.

What's the ultimate answer for you? Although there isn't an extensive body of research around meal timing to increase your calorie expenditures, the limited evidence available suggests that eating earlier in the day will both fuel your workouts and boost your fat-burning metabolism.