Weight loss: do meal timing, fewer meals or intermittent fasting work?

Worldwide, one in eight people live with obesity. This matters because carrying excess body fat raises the likelihood of type 2 diabetes, heart disease and some cancers.

Changing your diet plays an important part in managing obesity and avoiding weight gain. This can involve cutting calorie intake, adjusting eating habits and making healthy foods a priority.

But does any particular approach make weight loss more successful? Our latest research compared three weight-loss strategies to determine whether any produced greater weight loss than the others:

• changing calorie distribution – consuming more calories earlier, rather than later, in the day
• eating a smaller number of meals
• intermittent fasting.

We examined data from 29 clinical trials including almost 2,500 participants.

Over 12 weeks or longer, we found that all three approaches produced comparable weight loss: 1.4–1.8kg.

Therefore, if you want to lose weight, it is best to select an approach that fits your circumstances and lifestyle.

Eating earlier in the day

When metabolism is not working as it should, the body cannot respond properly to the hormone insulin. This may cause weight gain and fatigue, while also increasing the risk of several chronic conditions, including diabetes.

Eating more heavily later in the day – such as having a substantial evening meal and snacks late at night – appears to worsen metabolic function. In other words, the body is less effective at turning food into energy, controlling blood sugar and regulating fat storage.

By comparison, eating more calories earlier in the day seems to support better metabolic function.

This may not apply equally to everybody, however. Some people naturally have an evening "chronotype", meaning that they wake and remain awake later.

Those with this chronotype seem to be less successful at losing weight regardless of the approach they use. A range of factors may explain this, including genes, a greater chance of having a generally poorer diet and increased levels of hunger hormones.

Eating fewer meals

Missing breakfast is widespread, but does it make weight loss harder? Or is it preferable to have a larger breakfast followed by a smaller evening meal?

Although eating frequently may lower disease risk, recent research indicates that having six meals a day may lead to greater weight-loss success than eating one to two meals daily.

Yet this does not match the wider body of research, which generally indicates that fewer meals can produce more weight loss. Our findings suggest that three meals per day is preferable to six. The simplest way to achieve this is to remove snacks while retaining breakfast, lunch and dinner.

Most research compares three meals with six, and there is little evidence about whether two meals are better than three.

Nevertheless, concentrating calories earlier in the day – by eating most of them between breakfast and lunch – seems to be more effective for weight loss and could also reduce hunger during the day. Longer studies are still required.

Fasting, or time-restricted eating

Many people eat across a period exceeding 14 hours each day.

Late-night eating can disrupt the body’s natural rhythm and change the way organs work. In time, this may raise the risk of type 2 diabetes and other chronic illnesses, especially for shift workers.

Time-restricted eating is a type of intermittent fasting in which all calories are eaten within a six- to ten-hour period of the day, when people tend to be most active. It does not involve changing what you eat or how much you consume, but instead changing when you eat.

Research in animals indicates that time-restricted eating may result in weight loss and improved metabolism. Evidence in people remains limited, though, particularly regarding longer-term benefits.

It is also uncertain whether the advantages of time-restricted eating arise from the timing itself or from people simply consuming less overall. In studies we assessed, participants were able to eat freely, with no deliberate calorie restriction, while following an eight-hour daily eating window. They nevertheless naturally ate around 200 fewer calories each day.

What will work for you?

Previously, clinicians viewed weight loss and preventing weight gain as a simple equation of calories in and calories out. However, the way calories are spread across the day, meal frequency and late-night eating may also affect metabolism, body weight and health.

There is no effortless way to lose weight. Instead, choose the method – or combination of methods – that suits you most. You could consider:

• trying to eat within an eight-hour window
• eating calories earlier in the day, with an emphasis on breakfast and lunch
• choosing three meals a day rather than six.

The average adult gains 0.4 to 0.7 kg each year. Improving diet quality is vital for preventing this weight gain, and the strategies above may help as well.

Finally, much remains unknown about these eating patterns. Many available studies are short, involve small samples and use differing methods, which makes direct comparisons difficult.

Further research is under way, including carefully controlled trials with larger samples, more diverse populations and consistent methods. Hopefully, future research will provide a clearer understanding of how changing eating patterns can improve health.

Hayley O'Neill, Assistant Professor, Faculty of Health Sciences and Medicine, Bond University and Loai Albarqouni, Assistant Professor | NHMRC Emerging Leadership Fellow, Bond University

This article is republished from The Conversation under a Creative Commons licence. Read the original article.