Fat loss: Should you be exercising on an empty stomach?

Will working out on an empty stomach put you on the fast track to weight loss?

Like most fitness questions, and subsequent answers, this one falls in the grey area. 

Following the research published in the Journal of the International Society of Sports Nutrition, the answer would be no.

In their study, 20 women were divided into two groups. Three days a week for 60 minutes, both groups performed steady-state cardio on a treadmill. Before the workout began, one group consumed a meal-replacement shake, while the other jumped right into their routine with nothing in their gut.

After four weeks, researchers found both groups had shed the same amount of weight.

"There's a belief that when you exercise on an empty stomach, your body burns fat for fuel instead of the food you've just ingested," explained lead researcher Brad Schoenfeld, Ph.D. "But there's no evidence to support that fasted cardio has any benefit for fat loss."

However, according to a similar study done by Northumbria University published in the British Journal of Nutrition, researchers found the answer to be yes.

Twelve men completed a cardio workout on a treadmill having either eaten breakfast or still fasting from the previous night's meal.

The participants using fasted cardio burned up to 20 percent more body fat than their nourished counterparts.

“Exercise increases the total amount of energy we expend and a greater proportion of this energy comes from existing fat if the exercise is performed after an overnight fast,” researcher Javier Gonzalez said of the results. 

So, what gives? Why the discrepancy?

Well, Northumbria’s results may have been the byproduct of a suppressed appetite.

After each subject completed their workout, they were given pasta and told to eat until “comfortably full.” 

The researchers discovered the group that exercised fasted didn’t compensate for missed meals by consuming additional calories during lunch, nor did they complain of an increased appetite for the remainder of the day.

The accurate answer seems to be: it’s a matter of preference. Nevertheless, if you fuel up before a workout, make sure you’re eating the right foods. 

“For the most part, my recommendation is to eat balanced,” Roger Dickerman, personal trainer and co-owner of Relentless Fitness, said. “So one classic, people approved workout fuel would be almond butter, banana, scoop of protein. My philosophy revolves around a positive source of protein, positive source of carbohydrate, positive source of fat, and there’s no better way to represent that before a workout than exactly that formula.”

If you’re still interested in giving fasted cardio a crack, Jim Stopani, Ph.D. suggested it in a recent article published on Bodybuilding.com for “men with body fat in the low single digits (5-6 percent) and females with body fat in the low teens (13-14 percent), especially if they have specific problem areas like the lower back or thighs.”

In case you don't fall into that demographic – and for the impatient bunch looking to burn fat in the fasted possible manner – Dickerman has outlined an exercise routine to follow.

“Get a big strength workout in a week and make sure you get a big sprint workout in a week,” he said. “Where with the strength workout your pushing your limits on the type of weight that you’re able to push, pull, squat, and deadlift. And then on your sprint workouts, you’re working shorter, but super high intensity. So, like 30 (seconds) on, a minute off, eight times, but every time you’re doing that 30 on, toward the end of that 30 you’re really struggling.” 

Wait, weight loss results from only two workouts per week?

“I think people usually start too fast with too much. Prove to me you can do two workouts a week first. This is going to give your body a chance to get sore, tear itself down, recover, and get back to it with strength.”