Intermittent fasting is championed by celebrities and CEOs alike for its weight loss and health benefits. While there is promising evidence that fasting can help our bodies repair and perhaps extend our lifespans, it might not be the best approach for losing weight, and dietitians urge caution before cutting out meals.
Intermittent fasting is a type of time-restricted diet in which fasters leave a long gap between their last meal of one day and first of the next, compressing their meals into a shorter period during the day. Typically, fasters try to leave a gap of 16 hours without food and eat during an eight-hour window. Intermittent fasting is not the only type of time-restricted diet. Others like the 5:2 diet (in which dieters eat a normal amount of food for five days before two days of eating only 25% of their usual calorie intake) focus more on the amount of food consumed, rather than the time between meals.
“Time-restricted feeding is used as a weight loss tool, but it’s not my favourite approach,” says Rachel Clarkson, founder of London-based consultancy The DNA Dietitian. “You reduce calories but you don’t learn the essential behaviour change around what you’re putting into your body.”
Clarkson says that without learning what a healthy diet looks like people gain weight again when they stop fasting. “If it means you are feeling starved and restricted then the next day you might over-eat.
So, intermittent fasting might not be the right approach for people seeking weight loss, but there might be other reasons to change your eating patterns. Fasting is linked to a process called autophagy, which is attracting a lot of interest for its potential health benefits.
Autophagy is the process by which the body starts to recycle the structures inside its cells, including the nucleus, where DNA is stored, the mitochondria, which synthesise the chemical our cells use for energy, and lysosomes, which remove waste from our cells. In doing so, the cell can remove defunct structures, freeing up new raw materials from which new cellular structures can be built. Some of the new raw material might be used to make cell-protective proteins that further extend the lifespan of cells.