Are there any benefits to exercising on an empty stomach?
The idea of working out without any food in your belly seems to make logical sense. With no energy to burn off, surely you'll be attacking your fat stores when you exercise on an empty stomach, right?
It terms of the science, it's a debated subject with no clear answer.
The Japanese have long-followed a ritual of drinking water on an empty stomach for its health benefits; something that has now trended to the West.
Supposedly, when you down several glasses of water on an empty tummy – and then don't eat anything for the following hour or so – you'll flush out the toxins via your lymphatic system, helping increase the production of new muscle and blood cells and up your overall immune function.
It's also thought to stimulate your bowels for regularity, improve your metabolism for the day ahead, help with heartburn, the kidneys, and bladder infections, and even give you better skin, hair, and nails.
If this all sounds like something you'd hear in a TV commercial at 3am, it's because it is as sketchy as it sounds. There's no good research out there to link the empty stomach/water consumption theory. Drinking lots of water (in general) does come with health benefits, but there's no solid proof that you need to have a bare belly to receive them.
The question or whether or not it's a good idea to exercise on an empty stomach is a contentious one. Numerous studies do show that it's beneficial for weight loss.
Overweight people seem to respond better in terms of weight loss when it comes to working out on empty. A University of Bath study, for example, found that a one-hour walk with no food in your stomach activates metabolism genes to increase the rate at which stored fat burns, in comparison to those who did the walk after a carbohydrate-laden breakfast. Fit people also see similar, but smaller, benefits.
However, other studies – like this one from the Journal of the International Society of Sports Nutrition – show that people lose approximately the same amount of weight during a one-hour exercise regimen whether they have any empty stomach or not.
This brings up the "fed versus fasted" debate. Some interesting studies have been done on fasting (i.e. not eating for 8-12 hours) to see how it changes the body's metabolic parameters of the body change. This interesting research by University of Sfax, Tunisia and New Zealand's Massey University looked at physically-fit men during Ramadan and found both their body weight and their body fat percentage dropped when they exercised during a fast, as opposed to those who ate before working out.
This empty stomach approach has its downsides though. Naturally, eating before exercise gives you energy to complete the work-out. Many people struggle to push hard if they are on an empty stomach, which would mean less physical exertion, and less calories burned in a session. Moreover, a study in Appetite journal found that those who exercised on a full stomach had less urge to eat more food later. That is, when you exercising while starving and then need to quickly fuel your body when you're finished sweating it out, you may be so famished that you eat far more than you need to. The result? Excess calorie consumption.
Although not eating makes some people irritable, there's some good evidence to show that it can make you more productive. According to researchers from Yale University and the British Neuroscience Association, the stomach hormone that stimulates hunger when you have an empty stomach also promotes new brain cell growth. It's said that this process makes you feel sharper by enhancing cognitive processes, while also enabling the brain to better retain new memories.
With all this said, whether or not you can happily go about a portion of your day on an empty stomach is up to the individual. A lot of people feel lighter and more alert when slightly hungry, others have no energy at all and cannot concentrate. The jury remains out on whether or not exercise results are increased on an empty stomach, so it's up to you to find out what works best for your own system.
Written by Lee Suckling. Republished with permission of Stuff.co.nz.