Weight management in sport: more evidence for the benefits of time restricted feeding

As we have previously reported in Sports Performance Bulletin, there’s good evidence that restricting food intake timing (but not amounts or type) to an 8-10 hour window within each 24 hours can result in significantly enhanced fat loss, while still allowing training to continue as normal. Now a newly published study in the Journal of Nutritional Science [Journal of Nutritional Science 2018. Vol 7, e22], which you can read in full here (just click on the PDF icon to download) provides further evidence for this effect, but this time with far more modest time restrictions.

Ninety minutes later and earlier

In this study, participants were split into two groups — those who were required to delay their breakfast by 90 minutes and have their evening meal 90 minutes earlier, and those who ate meals as they would normally (the controls). Participants were required to provide blood samples and complete diet diaries before and during the 10-week intervention and complete a feedback questionnaire immediately after the study. Participants were not asked to stick to a strict diet and could eat freely, provided it was within a certain eating window. This helped researchers assess whether this type of diet was easy to follow in everyday life.

The findings

Researchers found that those who changed their mealtimes lost on average more than twice as much body fat as those in the control group, who ate their meals as normal. Another finding was that although there were no restrictions on what participants could eat, researchers found that those who changed their mealtimes ate less food overall than the control group. The researchers went onto comment that ‘if these pilot data can be repeated in larger studies, there is potential for time-restricted feeding to have broad health benefits’.

What’s going on?

How is it that simply delaying breakfast by 90 minutes and having an evening meal 90 minutes early could result in significantly more fat loss? The explanation is almost certainly related to the ‘thrifty gene’ effect. This effect arises because humans have evolved to switch on fat-burning genes (for energy and survival) when food is scarce.

Our ancient hunter-gatherer ancestors would not have had 24/7 access to copious food quantities; there would have been regular periods when food was not available. The ability to efficiently oxidise fat stores for energy was therefore paramount. The reasoning behind time restricted food intake is that by ensuring there are reasonably long periods in the day when no food is available to the body, it increases the activity of these thrifty genes (which we still have in our DNA). If breakfast is delayed by 90 minutes, and the evening meal is brought forward by 90 minutes, the overnight fast is lengthened, helping this ‘thrifty gene’ activation process.

You can read an in-depth article on the theory and benefits of time-restricted feeding, and how to apply it within a training programme, in the article link shown below.

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