“FASTING” DIETS have been on every magazine cover in the checkout line for some time now. They’ve also received a lot of attention on TV and the internet and generated considerable buzz on social media. As with any new diet trend, it’s important to know the facts about fasting before jumping in with both feet. So, let’s take a closer look at this approach to eating.
Intermittent fasting is touted as a good way to manage weight, heart disease, type 2 diabetes, and sleep problems. Some studies even suggest that fasting may slow the aging process. We’ve talked about the “magic bullet” in the past—could this be what people have been searching for? Though many studies have been done on fasting, the science and research is still limited in this area, so we can’t really justify that claim. Still, interest in fasting is growing and internet searches for the topic have climbed into the millions, so let’s take a deeper look at this diet phenomenon.
Intermittent fasting can take several forms, including:
1. Alternate-day fasting involves rotating days of eating and fasting. On fasting days, no food or beverages with calories are consumed. Calorie-free drinks like water, black coffee, and tea are permitted. On non-fasting days you can eat whatever you want, though healthy food choices are encouraged. In theory you are supposed to cut the number of calories you typically eat by 25 to 50%, thus achieving weight loss over time.
Wondering whether this really works? Well, studies show that the hunger on fasting days can be pretty overwhelming and the calories consumed on nonfasting days almost doubles because of the extreme hunger. Long-term effects have not been studied.
2. Modified or periodic fasting refers to cutting calories drastically (usually limiting calorie intake to less than 500 on fasting days) on two to three days a week and then eating normally on the other four to five days. Again, there are not enough studies to show whether this form of fasting is effective for weight loss.
3. Time-restricted fasting limits the intake of calories primarily to normal waking hours. The goal is to fast for eight to 12 hours, usually while you are sleeping. This pattern is good for people who enjoy—or have a habit of—snacking in the evening after dinner or even getting up during the night to eat. Once again, the jury is still out on this one. However, if you do tend to consume significant calories at night (nocturnal eating), it may be a problem and contribute to weight gain.
4. Of course, some religions and cultures encourage days or periods of fasting, though this is usually done for spiritual purposes rather than to achieve weight loss or other health benefits. Typically, they give exemptions to the elderly, young children, pregnant women, women who are lactating, etc. They also usually encourage adherents to get adequate hydration and eat small, sensible meals when allowed.
Intermittent fasting does work for some people, so how can you determine whether it’s the right choice for you? Many factors come into play. For instance, if you’re someone who gets shaky, “hangry,” or dizzy when skipping meals, you might want to try a different diet approach. Researchers also say that timing your eating to your natural circadian rhythms is best for health. Personal preferences, genetic makeup, environmental factors, and health factors all need to be taken into account as well. A lot more research still needs to be done. The most important thing is to eat in a way that works for you.
Also note that fasting does pose health risks for certain individuals, for example those with diabetes, those with a history of eating disorder or disordered eating, and women who are pregnant or lactating. Anyone considering fasting should talk to their physician first as medications may need to be adjusted.
Laurie Syring, RD/LD, is Clinical Nutrition Manager at ProMedica Flower Hospital.
