We often talk about the types of foods we should be including to optimise health and longevity. More research, though, is emerging on the benefit of intermittent fasting (IF) or time-restricted feeding (TRF) for improving metabolic markers such as insulin sensitivity (a risk factor for type 2 diabetes and heart disease), cholesterol levels, and blood pressure. Research also shows benefit for weight loss, a positive impact for those in remission from breast cancer, and it can help with regulating appetite.
The optimal time to fast (morning or night) and whether or not the benefits of TRF come from reducing calories and not the fasting window per se is a hot topic for discussion. Research shows that from first sip to last bite, people generally eat across 15 hours in a day, whereas when TRF you may only have between 6-8 hours to consume your daily intake. This makes it almost impossible for most people to consume the same amount of food and the subsequent calorie deficit results in weight loss — which in itself provides many of the health benefits I listed above.
So, then, is it the time spent not eating, or the weight loss that occurs from not doing so that is the driver of the improvements in health? A recent study was designed to test that theory with two groups: one where the participants ate their meals between 8am and 8pm, and another group that was restricted to eating between the hours of 8am-3pm. The researchers carefully controlled the number of calories eaten by study participants, so by the end of the study, there was no weight loss in either group.
In the absence of any changes to weight, and compared to the standard eating pattern, the participants following the TRF pattern had a lower insulin level post-meal, improved insulin sensitivity, increased pancreatic cell functioning (important for type 2 diabetes risk), lower blood pressure, reduced oxidative stress and reduced appetite in the evening.
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So what’s the key take-home message? The beneficial impact of TRF doesn’t just come from caloric restriction, and the time we spend not eating may be as important as the food we consume when we do.
Nutritionist Mikki Williden helps people manage their diets in an interesting way, at a low cost. Find out more at mikkiwilliden.com