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Three square meals a day used to be the definition of healthy eating. But no more. Research shows that skipping meals here and there turns on longevity genes and can lead to a longer and healthier life.
A growing body of studies in animals have shown that drastically restricting calories or fasting extends lifespan and improves age-related diseases. But it wasn't clear whether people could achieve the same results.
After all, fasting on a long-term basis or restricting calories over a period of years would be a difficult lifestyle for most people to maintain.
But researchers from the University of Florida have found an effective alternative to fasting or long-term caloric restriction. They call it the feast-or-famine diet. And they've found that for some people it mimics the same health and longevity benefits of traditional fasting.
The researchers recruited 24 people for a double-blind, randomized clinical trial. Their results were published in the journal Rejuvenation Research.[i]
For three weeks the participants alternated a day of "fasting" with a day of "feasting." On fast days they ate 25% of their normal daily calories. For a man, that meant about an average of 650 calories. Women ate slightly less.
An example of a fast day menu included roast beef and gravy, mashed potatoes, Oreo cookies, and orange sherbet. But here's the trick. They only ate one meal during the whole day.
On feasting days the participants ate 175% of their typical daily calories or about 4,550 calories for a man.
Feasting meals included bagels with cream cheese, oatmeal with honey and raisins, turkey sandwiches, apple sauce, spaghetti with chicken, yogurt, lemon pound cake, vanilla ice cream, and even Snickers bars and soda.
Averaged over the two days, the participants were eating a total of their regular daily calories. But the change in timing of those calories had a major impact on the measures of their health.
The researchers measured the participants' changes in weight, blood pressure, heart rate, glucose levels, cholesterol, markers of inflammation and genes involved in protective cell responses over 10 weeks.
They found that the intermittent fasting caused a decrease in insulin levels.
And it also caused a slight increase to SIRT3, a gene known to promote longevity. It's also involved in protective cell responses.
The SIRT3 gene encodes a protein also called SIRT3. The protein SIRT3 belongs to a class of proteins called sirtuins. Prior studies showed that if sirtuins were increased in mice, it extended their lifespan.
Researchers believe SIRT3 proteins are activated by oxidative stress from free radicals triggered by fasting. When the body undergoes fasting, low levels of oxidative stress trigger the SIRT3 cycle. In other words, free radicals are beneficial in turning on the SIRT3 longevity genes.
So what happens when your body has lots of antioxidants around to fight off free radicals and oxidation?
The researchers tested the effects of antioxidant supplements by repeating the feast and famine diet but including vitamin C and vitamin E supplements.
They found that some of the benefits of fasting disappeared. As perverse as it sounds, antioxidants neutralized the benefits of fasting. It seems that low levels of oxidative stress help the body trigger its own protective processes.
This is consistent with other research that found that flooding the system with antioxidant supplements may counteract the effects of fasting or exercise. The researchers believe that you need some inflammation or oxidative stress to trigger the body's regeneration or repair functions.
Intermittent Fasting Regenerates Brain
Overeating is a risk factor for age-related cognitive impairment. In animal models of Alzheimer's, Parkinson's, and Huntington's disease restricting calories increased the resistance of brain cells to malfunction and death.
Cutting calories seems to boost the protection of neurons by increasing production of proteins that suppress oxidation and free radicals.
It also increases the number of newly-generated neural cells in the adult brain. In other words, it may increase the brain's capacity for self-repair.
Researchers suggest that limiting calories may reduce both the incidence and severity of neurodegenerative disorders in humans.[xiii]
Caloric restriction has also been shown to improve insulin sensitivity in obese men. Animal studies show it may prevent or lessen the severity of cancer, stroke, coronary heart disease, autoimmune disease, and allergy.[ii]
Think you'd like to try the feast or famine diet? Be aware that most of the participants in the study found that fasting was easier than feasting. Even though it sounds strange, the researchers had a hard time getting people to eat enough on feast days.
But you don't really have to fast every other day. A couple of days a week of reduced calories may do the trick.
Intermittent Fasting Doubles Weight Loss
Intermittent fasting can also help you lose weight. Dr. Michael Mosley popularized an intermittent diet called the "5:2 plan." He describes it in his book book The Fast Diet: Lose Weight, Stay Healthy, and Live Longer with the Simple Secret of Intermittent Fasting.
His plan calls for eating regular meals 5 days a week and fasting 2 days every week. But "fasting" means eating 25% of your normal calories. That's about 600 calories for men and 500 calories for women.
It works by putting you into a fat-burning zone. Your body burns off sugar stores from your last meal for the following 8 to 12 hours. Then it starts burning off fat stored for fuel. If you eat every 6 or 7 hours, you're always burning carbs and never get to burning fat.
English researchers tested the plan in 115 dieters. Half of them cut calories every day. The other half ate regularly 5 days a week and ate only about 600 calories 2 days a week. After three months, the fasting group lost twice as much weight as the calorie-cutting group that reduced food intake every day.[iii]
If intermittent fasting sounds too daunting, you could try fasting for a shorter period every day. Start by closing the kitchen after dinner. If you eat nothing between 8 pm and 8 am you're already fasting 12 hours a day.
To take it a little further, try eating only between 11 am and 7 pm a couple days a week.
But don't let yourself feel weak or hungry. Fasting is not the same as starvation.
And don't forget food quality still counts. Snickers bars and sodas might not be the best choices on your feast and famine diet.
To learn more, check out GreenMedInfo's page on fasting and caloric restriction.
[i] Martin P Wegman et al. "Practicality of Intermittent Fasting in Humans and its Effect on Oxidative Stress and Genes Related to Aging and Metabolism." Rejuvenation Research, 2014; 141229080855001 DOI: 10.1089/rej.2014.1624
[iii] Harvie M et al, "The effect of intermittent energy and carbohydrate restriction v. daily energy restriction on weight loss and metabolic disease risk markers in overweight women." Br J Nutr. 2013 Oct;110(8):1534-47. Pubmed 23591120