In recent years intermittent fasting (IF) has grown in popularity. It’s an eating plan which alternates between states of fasting and windows of eating. Intermittent fasters repeat this pattern, depending on the type of program they’re doing, every day (16:8) or twice a week (5:2).
The idea behind it is that by giving your body a break from eating, it provides a chance to use stored energy, which can lead to health benefits like weight loss. And while trials have shown an IF diet can lead some to shed the kilos, what do we know about other health effects?
In a randomised controlled trial, around 50 people were divided into two groups. One group followed an IF diet for six months, while the other ate their usual diet. In the second six months of the trial, the people on their usual diet switched to intermittent fasting, so all trial participants were now on IF. The researchers were testing to see the effect of IF on various metabolic and molecular markers of healthy ageing – particularly C-reactive protein, a substance in the blood that can be a sign of inflammation in the body (which in turn can indicate one’s speed of ageing and risk of things like heart disease, stroke and dementia).
The researchers found that an IF diet did have a significant impact on bodyweight. Most participants were overweight when starting the trial and afterwards had lost up to seven kilograms or eight per cent of their total body weight. But weight loss didn’t come with a corresponding decrease in inflammatory markers – there was not a change over time in the C-reactive protein or other similar markers of ageing and metabolic health. That’s significant because when you lose weight by other methods, such as changes in nutrition or more exercise, you do also see a reduction in inflammatory markers. So, while there is weight loss associated with an extended IF diet, it may not achieve all the benefits seen by weight loss occurring via other means.
The study shows that while IF can help with weight loss goals, it’s likely not just to be how you eat – but what you eat. Research has shown that if the food you eat on these diets is Mediterranean in style, namely cooking with extra virgin olive oil, not much red meat and a large variety of vegetables, then you can get the metabolic benefits of the weight loss.