Could a 12-hour fast improve your health?

Time-restricted eating – which is a form of intermittent fasting – is a common way people try to shed some weight.

Recent research says it may make little difference to weight loss. But could it still improve your health?

The idea is, you leave a gap of at least 12 hours – ideally more – between meals on a regular basis (overnight, for instance), according to Dr Adam Collins, associate professor of nutrition at the University of Surrey.

There are other forms of intermittent fasting too, including the 5:2 approach, where you restrict your calorie intake for two days of the week and then eat normally on the other five. The 4:3, or 'every other day', involves similar restrictions on alternate days.

"Whichever one you choose, make sure you're doing it consistently," Collins advises.

No regime will be right for everyone all the time, says Collins: "So much depends on what you eat and, to some extent, when you eat it.

"It also depends on whether you're going to follow eating with activity or inactivity, and whether you've accumulated lots of calories throughout the day."

Another contributing factor is your circadian rhythm, external – natural cycles of sleep and activity based on cycles of light and dark.

Scientists are investigating whether eating out of kilter with your circadian rhythm – having a large meal at night when your body is signalling for sleep – is not optimal for health, external.

Regular breaks between eating give our bodies time to carry out valuable 'housekeeping', according to Collins.

After a meal, the glucose from carbohydrates in food is used for energy – either immediately or stored for later. In a fasted state, which can start 10–12 hours after your last meal, the body has less of this form of glucose.

So the liver begins to break down stored fat into fatty acids called ketones, external to use as fuel instead. This process is known as metabolic switching, external and is a reason why, previously, fasting has been linked to weight loss.

But while some of the latest research questions whether fasting actually does have an impact on weight loss, external, there is evidence it may come with other benefits – like potential improvements to your gut microbiota, external.

The problem is, most of us are too full for too much of the time to experience these benefits, says Collins.

Eating three meals a day plus snacks means we're in a "constantly fed state". As a result, our bodies continuously process new intakes of food instead of dealing with fat reserves.

"All the things we associate with poor metabolic health and disease risk – cardiovascular disease, insulin resistance, diabetes and low energy – are essentially a manifestation of fuel mismanagement," he says. "Eating in a grazing pattern means you're not able to store, liberate and utilise fuel in the right way."

Short periods of fasting (which you can do by having breakfast later or dinner earlier, for instance), may benefit your gut microbes, explains professor Tim Spector of King's College London in his book Spoon-Fed.

Evidence suggests that during fasting, certain species of microbes replicate and feed off carbohydrates in the gut lining, making the gut barrier (which plays a role in the immune system) healthier and more efficient.

Researchers believe this could improve your mood and energy levels in the short term and possibly lead to weight loss in the longer term.

Chronic inflammation is linked to heart disease, external, type-2 diabetes, cancer, multiple sclerosis, inflammatory bowel diseases and other conditions, external.

Some experts believe intermittent fasting has the potential to manage or prevent chronic inflammation, external. The idea is that ketones produced during fasting improve your cells' ability to suppress inflammation and repair damage.

"From a metabolic point of view, we definitely see benefits in intermittent fasting," says Collins.

"You're better at clearing, storing and utilising carbs and fat [when you're intermittent fasting], so there are improvements in insulin sensitivity, blood lipids (fats) and other cardiovascular risk factors."

Such improvements are evident in lean people as well as those who are overweight, he says.

This is possibly because people of a healthy weight can still carry harmful deposits of fat in their internal organs, says Collins.

Fasting is a highly complex area, where research is ongoing and robust clinical trials are lacking, according to Collins.

The New England Journal of Medicine study, external suggests intermittent fasting might be useful in treating diseases including Alzheimer's and Parkinson's, slowing the growth of some cancers, repairing tissue damage and enhancing athletic performance.

Krista Varady, professor of nutrition at the University of Illinois says, "There's good evidence to show the 'every other day' and 5:2 diets are the most effective fasting patterns for weight-loss and health benefits. But she urges caution.

"Many of the claims about the benefits of intermittent fasting are overblown," she says. "A lot of the results of studies on animals just haven't been replicated in humans."

Emerging evidence suggests that regular periods of fasting may have health benefits beyond weight loss, but the science is not yet proven.

Intermittent diets are not suitable for people at risk of, or with a history of, eating disorders or anyone underweight.

Diabetics and those with a pre-existing medical condition should seek medical advice before undertaking any form of fasting.

Want more? Visit BBC Food on Instagram, external, Facebook, external and Pinterest, external or watch the latest Food TV programmes on BBC iPlayer.