Taking a ‘diet holiday’ could improve weight loss

Researchers from the University of Sydney and Garvan Institute of Medical Research have good news for people who have trouble sticking to their diet: taking a break from dieting won’t necessarily ruin your weight loss efforts, and it could actually improve them.

Conducted in mice and published in the journal PLOS ONE, the research found that taking a break from dieting could help weight loss by improving the efficiency of weight loss (the amount of weight lost for every kilojoule restricted).

“Our study suggests that if you’re trying to lose weight, then taking a break from dieting could give you better bang for your buck in terms of the amount of weight you lose relative to the effort you put in,” said lead author Associate Professor Amanda Salis, from the University’s Boden Institute for Obesity, Nutrition, Exercise & Eating Disorders at the Charles Perkins Centre.

“Existing research suggests that this phenomenon will also apply in humans. We are currently conducting clinical weight loss trials to confirm this, in collaboration with Bond University, the University of Queensland, and Queensland University of Technology.

“As anyone who has ever tried to lose weight can attest, sticking to a long-term, kilojoule-restricted diet – which is required to achieve lasting, clinically significant weight loss – is notoriously difficult. We are hopeful that this research could lead to improved and more sustainable weight loss strategies,” Associate Professor Salis said.

The research team followed obese mice that were fed one of two kilojoule-restricted healthy diets for 12 weeks. One diet continuously provided 82 per cent of normal kilojoule intake, while a second, intermittent diet provided 82 per cent of normal kilojoule intake for five to six consecutive days, followed by unrestricted intake for one to three days. There was no difference in body weight, fat mass, circulating glucose or insulin concentrations, or the insulin resistance index at the end of the 12 weeks, but weight loss efficiency was more than two times better on the intermittent diet than on the continuous diet.

“When mice on the intermittent diet were allowed to bust out and eat as much healthy food as they wanted for those one to three days, they ate up to 70 per cent more than usual, and up to 40 per cent more than non-dieting mice, resulting in an overall 12 per cent greater intake compared to mice on the continuous diet. However, they lost just as much weight and body fat,” Associate Professor Salis said.

“So it seems that – for mice at least – there’s no need to be the dux of the diet club and follow a weight loss diet to the letter in order to get results.”

Unlike popular intermittent fasting diets such as the five-two diet, in which people tend to eat less than normal even during the ‘feast’ phase of the diet, the approach used here involved a true break from kilojoule restriction – what Associate Professor Salis calls a ‘weight loss holiday’. The researchers hypothesise that this is a key feature of the intervention and the reason it resulted in better weight loss efficiency.

Associate Professor Salis said it was important to note that mice in the study were eating healthy food during their weight loss holidays, not junk.

“Eating an overall healthy diet is particularly important during weight loss efforts, because nutritional deficiencies, especially deficiencies in micronutrients such as calcium, iron, folate and zinc, are common among people with overweight and obesity, and this can be exacerbated by weight loss diets. So weight loss holidays can be an opportunity to get more nutrients into your body, thereby helping to reduce nutritional deficiencies.”

With the early months of the year bringing a flood of weight loss efforts, Associate Professor Salis advised dieters to heed the advice of the study and avoid ‘all or nothing’ thinking about weight loss.

“If you do find yourself sometimes eating more than you intended, it may not have any adverse effects on your overall progress, so don’t get discouraged – just get back on the wagon and keep going,” she said.

“If the results of this study apply in humans, as we predict they will, then when you return to a more careful diet after your weight loss holiday, your break could actually improve the efficiency of your weight loss.”

To participate in Associate Professor Amanda Salis’ clinical weight loss trials at the University of Sydney, email her team on tempo.diet@sydney.edu.au, or register your interest here.To participate in the team’s clinical weight loss trials at Bond University, click here. To find other clinical weight loss trials around Australia and the world, click here.