Intermittent fasting explained sort of

Intermittent Fasting (IM) is the new “It” diet. Actually the idea has been floating around for several years, but it’s picked up traction recently. Listening to the gushy reviews, you’d think it was the cure-all for obesity, aging and inflammation.

So what is it exactly? Well, that’s the $64 question. It seems IM has no standard definition. It’s whatever you want it to be, as long as you spend part of the day not eating. Actually, these days, that’s hard to do. We’re surrounded by readily available and ready-to-eat food and drinks, and we’re told that we should avoid being hungry no matter what.

Ironically, the whole point of IM is to become hungry. Very Hungry. For Hours. Here are some variations on the diet:

  • Alternate Day fasting: eat on one day during a set 12 hour period. Then do not eat anything at all for the next 36 hours (one whole day and through the next night)
  • The 5:2 Diet: 2 days a week you eat nothing. You eat normally the other 5 days.
    • Variation: You’re told you can “eat all you want” on those 5 days. Sometimes they’re called “feast” days.
  • Time Restricted Feeding, sometimes referred to as the 16:8 Diet: You only eat during an 8 hour window of opportunity everyday. You consume nothing but water for the other 16 hours.
  • Modified Fasting: You limit food intake to 20-25% of your usual intake on “fast” days.
  • One Meal A Day: Eat one big meal; don’t eat anything else until time for the next day’s big meal.
    • Variation: Two Meals A Day.

It’s not hard to imagine that if you follow any of these regimens you’re likely to become very hungry very often. But if you can cope with the frequent hunger, you may experience a number of health benefits such as:

  • weight loss, particularly fat loss
  • reduced blood lipids
  • improved insulin sensitivity and lower glucose
  • lower measures of inflammatory mediators

Various studies of IM show these effects. The catch is that for the most part, simple low calorie diets show the same effects. Any reduction in calorie intake leads to weight loss, and weight loss leads to improvements in risk factors.

What’s the appeal of IM diets if simple calorie restriction achieves the same goals? For some people, IM makes dieting more special, which motivates them to stick to the program. Others have been persuaded by diet gurus that intermittent fasting is different; it’s healthier that just cutting calories. There’s a belief that IM is an anti-aging strategy, although there’s no actual proof for that claim. Finally, an intermittent fasting schedule might fit into someone’s lifestyle better than daily calorie counting. They have days when eating very little, or nothing is OK; they can enjoy eating without restrictions on other days. No calorie counting needed.

How long can you do this?

While the research shows metabolic benefits, the studies have only been short term. Can someone stick to this indefinitely? People who drop out of IM studies say sticking to the diet is too difficult. And as I’ve said numerous times previously: if you can’t stick to a diet, it doesn’t matter how wonderful it looks on paper. It does not work for You. That philosophy is probably why lots of IM dieters just invent their own versions that do work. They just eat dinner. Or they eat very little on some days because that’s just how life goes.

Is IM safe?

There’s no evidence that IM diets are generally unsafe, although if you have any particular medical problems — Type 2 diabetes is one example — you should clear this with your doctor. Humans have lived through periods of fasting for eons. Before modern agriculture and food storage methods, ancient humans were at the mercy of food availability. Changing seasons or poor hunting might mean little to eat. Periodic fasting was the norm. Now we freak out if we can’t have a snack or a latte every hour.

Intermittent fasting regimens might serve as an effective way to get people away from a life of non-stop eating and drinking. And that’s a good thing, even if you don’t lose a lot of weight.

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