Quinn on Nutrition: Fasting diets

January 18, 2016

"You didnít eat much for lunch," I commented to my daughter after I watched her down a small carton of yogurt before she rushed back to work.

"Today is my fasting day," she replied, reminding me that she limits herself to just 500 calories on Monday, Wednesday and Friday. 

"Oh, right," I said, remembering some recent articles about this style of eating.

Fasting diets are not new. One that has been around for a few years is the 5/2 diet which allows you to eat normally for five days a week and fast the other two. Itís called "intermittent fasting" (IF) or intermittent calorie restriction (ICR) ó a way to take in fewer calories from week to week.

"I limit myself to 500 calories on my fasting days," my daughter said. And on the other days, I try to stay around 1800 calories. So I average about 1200 calories a day. Itís just a different way of managing my calories."

Fasting does work. Any plan that prevents us from consuming fewer calories than our bodies require for energy will force us to use energy from within. Bloated fat cells are a great energy reserve, for example. Like a bank account, when we withdraw more than we deposit, the fund shrinks and we lose weight.

Does this approach of severely limiting calories on alternate days have any advantages over traditional calorie restricted diets? 

"I find that Iím not that hungry after my fast days," my daughter reported. "And on my non-fasting days ó when I supposedly can eat what I want ó I enjoy the taste of food more."

"Iím also more aware of how I used to snack unconsciously even when I wasnít hungry. Now I say ĎOops! I canít do that."

Any other advantages?

"What peaked my interest," she said, "was the Alzheimerís researchÖIím kind of worried about that." (Her grandfather had dementia from this progressive brain disorder.)

Indeed, some research (mostly in animals) has shown that ó in addition to weight loss ó low calorie diets and fasting on alternate days may help prolong the health of aging brains and prevent declines in brain function as we age.  

"Having intermittent fasting days also helps me understand real hunger... makes me more aware of my hunger signals. And itís not like Iím starving because Iím still getting 500 calories on my fasting days."

And then she said something that makes me realize she really did pay attention growing up with a dietitian mother. "I look for healthy ways to get the most nutrition bang for my calorie buck. Like I can have a nice piece of fish and a big serving of broccoli or cauliflowerÖversus three cookies." I smile.

A recent review article in the journal of the Federation of American Societies for Experimental Biology (FASEB) found that intermittent fasting diets ranging from 1 to 4 fasting days per week were indeed effective for losing weight and not gaining it back. Reported health benefits include lower blood pressure and blood sugar levels. And sticking to these diets may be easier since they allow some flexibility in eating. Hereís to choosing healthy calories.



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