If you’ve ever looked into intermittent fasting, a diet that requires followers to fast for 12 to 20 hours daily, you might’ve come across some dire warnings about the diet being really, truly, dangerously bad for women.
Women’s bodies are more sensitive to the signals of starvation, so going
too long without eating could throw their hormones out of whack, some experts
say. As a result, intermittent fasting can make you so ravenous that you end up
devouring everything in sight. Or worse, it can cause your body to break down
lean muscle for fuel.
A quick Google search of “intermittent fasting for women” will tell you
that the best way to avoid this supposed fate is with crescendo fasting—a
special type of fasting that works with our delicate lady hormones instead of
against them.
Instead of fasting 12 to 20 hours daily, crescendo fasters fast for 12
to 16 hours at a time on two to three non-consecutive days per week. (So, they
might stop eating at 7 PM and fast until 9 AM the next morning and then do the
same thing again a few days later.) The origins of the diet are murky, but it
seems to have a cult following among Paleo-leaning health blogs.
Folks who insist that women need to fast in a special way usually cite a
single study that was performed on rats. The rats were deprived
of food for a full day, every other day for 12 weeks. Just two weeks into the
experiment, the researchers found that the female rodents’ hormones were out of
whack, causing their periods to stop and their ovaries to shrink. Which,
admittedly, sounds pretty horrible.
Fasting for shorter, less frequent periods still restricts your calorie
intake to help you lose weight, but it doesn’t restrict calories enough to send
your body into starvation mode and cause the aforementioned hormonal changes to
happen. At least, that’s the logic used by proponents of crescendo fasting.
Related: 5 Types of Intermittent Fasting
Related: 5 Types of Intermittent Fasting
But is crescendo fasting actually a superior strategy? And are you doomed
to wreck your metabolism if you try any other type of fast to lose
weight? The answers to these questions below, plus everything else you need to
know before trying this weight loss method
There’s not
much research showing that women need to fast differently than men—and rats'
metabolisms do not match humans' perfectly.
“A rat only lives for a few years. So starving one for [24] hours would
be like starving a human for several days,” says Krista Varady, PhD, associate
professor of nutrition at the University of Illinois, Chicago, and author
of The Every Other Day Diet. At which point, a man or a woman’s
metabolism would slow down dramatically in an effort to conserve resources.
However, popular fasting diets don’t suggest cutting out food completely for
days, making the already shaky animal study even less applicable to humans.
As for the studies that have been done on humans? There’s not
much out there to suggest that fasting will mess with your hormones or turn you
into a fat storage machine, says Courtney Peterson, PhD, assistant professor of
nutrition at the University of Alabama at Birmingham. In a year-long,
randomized clinical trial, Varady and her co-authors found that
fasting didn’t impact obese women any differently than obese men. Alternate day
calories—in which subjects ate 500 calories every other day and ate normally on
the other days—helped both male and female subjects lose around 6% of their
body weight. (That translates to a 150-pound woman losing 9 pounds, or a
175-pound woman losing 10.5 pounds.)
However, one study from 2005 suggests that fasting could reduce
women’s insulin sensitivity slightly more than men’s, causing their blood sugar
to spike higher after a meal. Diminished insulin sensitivity also makes it
harder to digest carbs and absorb nutrients, increasing the odds of gaining
weight.
However, the study was short and small—it looked at eight women for just
two weeks. That’s not enough time to see how fasting really affects the body,
Varady says. “The first two weeks of intermittent fasting are a jumble, where
your body is trying to figure out what’s going on,” she says. And over the
course of a year, findings actually show that insulin sensitivity improves
with intermittent fasting." Experts don’t fully understand why, but it
could be that fasting lowers inflammation or improves insulin signaling
pathways, Peterson explains.
Related: Things To Know Before You Try Intermittent Fasting
Related: Things To Know Before You Try Intermittent Fasting
There are
plenty of ways to make a fast work for you.
If you want to give intermittent fasting a try, you don’t
necessarily need to pick a plan based on your sex. “There’s no scientific
research on crescendo fasting,” Peterson says. Instead, you should think about
what works best for your lifestyle so you can actually stick to it, recommends
Varady. Here’s how to set yourself up for success:
·
Pick a plan that seems doable. “There’s no scientific research on crescendo fasting,” Peterson
says. Instead, stick with one of the two types of intermittent fasting plans
that have been proven to help with weight loss—and think about which one
would work better for you. 5:2 fasting involves doing two day-long fasts per
week (i.e., eating no more than 500 calories), while time-restricted feeding
involves fasting for a period of 12 to 20 hours daily (like cutting off food
and caloric beverages completely at 6 PM and not eating again until
the next morning).
Shorter, daily time-restricted feeding fasts tend
to work better for most people, Varady says. In fact, subjects who fasted from
6:00 PM until 10:00 AM the next morning naturally cut about 300 calories daily,
found Varady in a new, yet-to-be published study.
·
Don’t cut your calories too much. Planning to go the day-long fasting route? You shouldn’t actually
go the entire day without eating—just cut your calories by a sizeable
amount. There’s no hard and fast recommendation for how much you should (or
shouldn’t) eat. But in general, studies have subjects consume around 25% of
their usual calorie intake on fasting days. For a woman normally eating 1,600
calories, that’s around 530 calories on a fast day.
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