by Dr Hayley O'Neill and Dr Loai Albarqouni
Globally, one in eight people are living with obesity. This is an issue because excess fat increases the risk of type 2 diabetes, heart disease and certain cancers.
Modifying your diet is important for managing obesity and preventing weight gain. This might include reducing your calorie intake, changing your eating patterns and prioritising healthy food.
But is one formula for weight loss more likely to result in success than another? Our new research compared three weight-loss methods to see if one delivered more weight loss than the others:
• altering calorie distribution – eating more calories earlier rather than later in the day
• eating fewer meals
• intermittent fasting
We analysed data from 29 clinical trials involving almost 2500 people.
We found that over 12 weeks or more, the three methods resulted in similar weight loss: 1.4–1.8kg.
So if you do want to lose weight, choose a method that works best for you and your lifestyle.
Eating earlier in the day
When our metabolism isn’t functioning properly, our body can’t respond to the hormone insulin properly. This can lead to weight gain, fatigue and can increase the risk of a number of chronic diseases such as diabetes.
Eating later in the day – with a heavy dinner and late-night snacking – seems to lead to worse metabolic function. This means the body becomes less efficient at converting food into energy, managing blood sugar and regulating fat storage.
In contrast, consuming calories earlier in the day appears to improve metabolic function.
However, this might not be the case for everyone. Some people naturally have an evening “chronotype”, meaning they wake up and stay up later.
People with this chronotype appear to have less success losing weight, no matter the method. This is due to a combination of factors including genes, an increased likelihood to have a poorer diet overall and higher levels of hunger hormones.
Eating fewer meals
Skipping breakfast is common, but does it hinder weight loss? Or is a larger breakfast and smaller dinner ideal?
While frequent meals may reduce disease risk, recent studies suggest that compared to eating one to two meals a day, eating six times a day might increase weight loss success.
However, this doesn’t reflect the broader research, which tends to show consuming fewer meals can lead to greater weight loss.
Our research suggests three meals a day is better than six. The easiest way to do this is by cutting out snacks and keeping breakfast, lunch and dinner.
Most studies compare three versus six meals, with limited evidence on whether two meals is better than three.
However, front-loading your calories (consuming most of your calories between breakfast and lunch) appears to be better for weight loss and may also help reduce hunger across the day. But more studies with a longer duration are needed.
Fasting, or time-restricted eating
Many of us eat over a period of more than 14 hours a day.
Eating late at night can throw off your body’s natural rhythm and alter how your organs function. Over time, this can increase your risk of type 2 diabetes and other chronic diseases, particularly among shift workers.
Time-restricted eating, a form of intermittent fasting, means eating all your calories within a 6-10 hour window during the day when you’re most active.
It’s not about changing what or how much you eat, but when you eat it.
Animal studies suggest time-restricted eating can lead to weight loss and improved metabolism. But the evidence in humans is still limited, especially about the long-term benefits.
It’s also unclear if the benefits of time-restricted eating are due to the timing itself or because people are eating less overall.
When we looked at studies where participants ate freely (with no intentional calorie limits) but followed an eight-hour daily eating window, they naturally consumed about 200 fewer calories per day.
What will work for you?
In the past, clinicians have thought about weight loss and avoiding weight gain as a simple equation of calories in and out. But factors such as how we distribute our calories across the day, how often we eat and whether we eat late at night may also impact our metabolism, weight and health.
There are no easy ways to lose weight. So choose a method, or combination of methods, that suits you best. You might consider:
- Aiming to eat in an eight-hour window
- Consuming your calories earlier, by focusing on breakfast and lunch
- Opting for three meals a day, instead of six
The average adult gains 0.4 to 0.7kg per year. Improving the quality of your diet is important to prevent this weight gain and the strategies above might also help.
Finally, there’s still a lot we don’t know about these eating patterns.
Many existing studies are short-term, with small sample sizes and varied methods, making it hard to make direct comparisons.
More research is underway, including well-controlled trials with larger samples, diverse populations and consistent methods.
So hopefully future research will help us better understand how altering our eating patterns can result in better health.
- Dr Hayley O'Neill is an Assistant Professor in the Faculty of Health Sciences & Medicine at Bond University. Dr Loai Albarqouni is an Assistant Professor in the Institute for Evidence-Based Healthcare at Bond University. This article was first published on The Conversation.