dieting 2 out of four weeks gets you to goal

On/Off Dieting Could Help Weight Loss ... But Takes a Little Longer

By Trudi Purdy, wlr team

Key Takeaways:

  • Taking regular, two-week breaks from dieting could help you lose more weight overall
  • It could help you keep the weight you have lost off

If you want to lose more weight and keep it off, but aren’t worried about how long it takes, then intermittent dieting could be for you according to Professor Nuala Byrne of the University of Tasmania.

Here's How it Works

Weeks 1&2Restrict Calories for a 2-week 'dieting' period

Weeks 3&4: Eat freely, but within the number of calories needed to maintain you at your current weight, for a 2-week non-dieting period

Repeat for as long as it takes to reach your weight loss goal. People on this study dieted for 16 weeks continuously, or 16 weeks over a 30-week period. 

Not to be confused with Intermittent Fasting diets ...

'Intermittent dieting' is different from most intermittent fasting (IF) type diets in that on an IF diet you essentially eat what you like, with no calorie limit, on non-fasting days. This difference could be quite significant, as you'll see below.

The Study

Professor Byrne and her team were investigating the body’s ‘famine reaction’ to continued dieting and how it impacts weight loss1.

For the study, 51 overweight men were split into two groups with both groups reducing their calorie intake by a third.

  • The first group did that continuously, over a 16-week period
  • The second group reduced their calories for two weeks and then took a two-week break where they ate enough calories to maintain their current weight

Both groups carried on like this until they had done 16 'dieting weeks'. This meant the intermittent, on/off, dieting group dieted for 16 weeks over a 30 week period.

The Results

  • The on/off dieting group lost, on average, 8kg more than the continuous group
  • They also kept more of the weight off at a 6 month follow-up

Byrne said,

“It seems that the ‘breaks’ from dieting we have used in this study may be critical to the success of this approach.”

She went on to say that, while further investigation into the intermittent dieting approach are needed, this study’s findings provided support that intermittent dieting is a better alternative to continuous dieting for long term weight loss.

"When we reduce our energy (food) intake during dieting, resting metabolism decreases to a greater extent than expected; a phenomenon termed 'adaptive thermogenesis' - making weight loss harder to achieve," Byrne said.

Famine Reaction

"This 'famine reaction', a survival mechanism which helped humans to survive as a species when food supply was inconsistent in millennia past, is now contributing to our growing waistlines when the food supply is readily available."

Byrne said while researchers in the past had shown that as dieting continued, weight loss became more difficult, this study looked more closely at ways to lessen the famine response and improve weight loss success.

Intermittent Dieting VS Intermittent Fasting

Byrne did point out that, although this two-week intermittent diet had proved successful in the study, other popular diets which include cycles of several days of fasting and feasting were not any more effective than continuous dieting2.

"There is a growing body of research which has shown that diets which use one to seven day periods of complete or partial fasting alternated with ad libitum food intake, are not more effective for weight loss than conventional continuous dieting."

It is useful to point out here that an ‘ad libitum’ food intake, essentially eat whatever/as much as you want, was not a feature of this intermittent dieting study.

Emperor surrounded by feast ad libitum
Ad libitum is Latin for ‘at one’s pleasure’ or ‘as you desire’

This may be a reason why intermittent fasting diets don't result in greater weight loss - the ad libitum days mean that overall calorie restriction is relatively small.

The 5:2 diet plan on wlr takes this into account, the plan includes meals for non-fasting days so you don't undo the good work you've done on fast days.

The intermittent group in this study took 2-week ‘breaks’ from severe calorie restriction, but still had to stick within their maintenance calories in non-dieting weeks.

Could This Approach Work for You?

People in the weight loss industry quite often talk about the famine response or starvation mode when reducing calories. There remains some controversy as to whether 'starvation mode' is actually a thing.

However, this study does seem to indicate that to combat the body’s adaptive thermogenesis response to reducing calories, and ensure continued and sustainable weight loss, taking regular breaks is successful.

That said, much more research is needed, and this was a small study.

You would need to weigh up whether the time it takes is the most important factor to you or whether intermittent dieting suits your goals.

Try 2 Weeks On/2 Weeks Off

The wlr goal setting facility makes this a breeze, simply set to maximum weight loss for two weeks, then maintenance for 2 weeks and follow the numbers ...

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1. Byrne, N., Sainsbury, A., King, N. et al. Intermittent energy restriction improves weight loss efficiency in obese men: the MATADOR study. Int J Obes 42, 129–138 (2018).

2. Trepanowski JF, Kroeger CM, Barnosky A, et al. Effect of Alternate-Day Fasting on Weight Loss, Weight Maintenance, and Cardioprotection Among Metabolically Healthy Obese Adults: A Randomized Clinical Trial. JAMA Intern Med. 2017;177(7):930–938. doi:10.1001/jamainternmed.2017.0936

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