Intermittent fasting

For some time now a new diet trend has been everywhere in the media: intermittent fasting. We looked into what it means, how it works, and what it can do for blood pressure.

{Fehler für :template{template="presse/pm2016_2_small" param1="presse/pm2016_3" param2="16:8 - 16 Stunden Fasten pro Tag"} Intermittent fasting, also called time-restricted or intermittent eating, is an eating pattern where you regularly have periods with no food intake. One common approach is the 16:8 method: you fast for 16 hours and eat during the remaining eight. Another is the 5:2 method, where you eat normally five days a week and fast eating nothing or almost nothing (up to about 500 kcal) on two days. A stricter version is alternate day fasting, where you fast every other day in that way.

Each of these approaches has the big advantage that this dietary approach is easier for most people to stick with than traditional diets. With the 16:8 method, skipping breakfast or dinner makes it relatively simple to extend the no-food period to 16 hours. Most people sleep through a large part of that time without eating. One example would be eating until 7:00 pm, skipping breakfast the next day, and then eating again from 11:00 am. Or you could have breakfast at 6:00 am, eat lunch, and start fasting at 2:00 pm until 6:00 am the next day.

If you eat as usual during the eating window and dont compensate by eating more, youll naturally consume fewer calories overall. That makes it relatively easy to create a calorie deficit, which leads to weight loss.

Besides the expected weight loss, intermittent fasting is also credited with generally positive effects on the body. The long break from eating stimulates autophagy (the body's own maintenance program). This process removes damaged or dead cells and cleans and renews others. Its basically the cells cleaning and repair squad. Autophagy also supports the immune system by eliminating pathogens that have entered cells.

This cell-cleanup program needs certain conditions in the body to work. Glycogen stores must be depleted and there must be no new carbohydrates available to fuel the cells. The fasting periods of intermittent fasting help bring this about. Physical activity also helps deplete the stores. However, fasting for too long over days or weeks has the opposite effect: it slows down cellular work because the cells lack the energy they need to clean and renew themselves.

Insulin also plays a role in autophagy. If you eat small meals frequently during the day, insulin levels stay fairly constant. But insulin inhibits autophagy. That means when insulin stays at a consistently high level, the cell-cleanup program cant run. To trigger autophagy, insulin needs to fall which happens when no more food is provided.

Many of the positive effects of intermittent fasting have so far been shown mainly in animal studies. Whether those results apply to humans is not yet clear we dont have solid data yet.

Besides the blood pressure improvements due to weight loss, a small study with eight overweight men who were also diagnosed with prediabetes found a blood pressure reduction independent of weight loss. The study isnt really representative because of the small number of participants and their health status. Still, its worth mentioning that participants who ate the same total calories in a shorter time window didnt lose the expected amount of weight, yet their blood pressure still fell. After five weeks of intermittent fasting, their systolic blood pressure had dropped on average by 11 mmHg and their diastolic pressure by about 10 mmHg. Their insulin metabolism also improved: there was less insulin being released after the observation period, which likely helped lower blood pressure as well.

Whether intermittent fasting is actually superior to other eating or diet approaches is debated. Theres still little long-term research. A 2017 study compared 100 metabolically healthy overweight people divided into three groups. One group followed traditional calorie restriction (75 percent of daily energy needs), the second followed alternate day fasting (25 percent of daily energy needs on fasting days and 125 percent on eating days), and the third ate as usual. After one year there were no significant advantages for either fasting group. Both groups lost about the same amount of weight.

So intermittent fasting is a method thats relatively easy for many people to implement to reduce overall calories and lose weight. You dont have to count calories or completely give up certain foods. That makes it easier for many to stick to the no-food periods. However, a clear advantage over daily calorie restriction has not yet been proven.

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Intermittent fasting

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