Why Intermittent Fasting Won't Help You Lose Weight

Intermittent fasting may seem to be every dieter's dream. After all, you only need to refrain from eating for a certain number of hours of the day — and yes, the time you spend sleeping does count! How sweet is that? Just keep hitting the snooze button ... As an added benefit, this will make you too late to take time for breakfast, so there's your morning, done. Just put off eating until lunchtime. Then, if you're following the popular 16/8 hour format, you'll have until 8 p.m. to satisfy your hunger, though no late-night eating or drinking is kind of a bummer.

There is also 12:12 version of IF that only requires fasting for 12 hours at a stretch (again, sleep is included), which would allow for some midnight snacking, assuming you'd put off your first meal until noon. There's even a 5:2 format that severely limits calories on just two days out of the week, while allowing you to eat around the clock on the other 5 (though Jillian Michaels says this last variant is "simply garbage"). While some variants on intermittent fasting, such as the Dubrow diet, do place restrictions on what you can eat during that restricted time window, others allow for a lot of leeway.

Nutritionist Alisa Vitti, founder of FLOLiving, notes that many claims regarding IF's supposed benefits come from what she calls "mostly male biohackers." Her concern is that this type of diet can be not only ineffective, but actually harmful for women.

Vitti cites research published in the Journal of the American Medical Association showing how time-restricted eating really doesn't work too well as a weight-loss method for women or men. She says that while many have claimed benefits from intermittent fasting including balanced blood sugar and prevention of diabetes and cancer, as well as weight loss, this study indicates that these claims aren't necessarily always based in reality.

It seems that both the men and the women who took part in this 12-week study " didn't lose significantly more weight than the control group." But what is even more unsettling is the fact that "the weight they did lose was primarily lean muscle mass, not fat," something that was not seen in the control group. "What's more," Vitti went on to say about the study results, "the researchers didn't observe any significant differences in fasting glucose, fasting insulin, HOMA-IR, and total cholesterol between the two groups."

While of course it would be possible to start your day of intermittent fasting by eating a big meal first thing in the morning and then simply stop eating early in the afternoon, most people just don't function that way. Most of us, if were we to follow a 16:8 eating plan, would find it far easier to pass on breakfast than dinner. Big mistake, says science (and Vitti agrees).

The American Journal of Clinical Nutrition (via Oxford Academic) published the findings of a 2014 study that concluded eating breakfast is associated with overall lower body weight, and that skipping that meal will do little to promote weight loss. Vitti also adds that, based on her analysis of their findings, "a good breakfast filled with high-quality protein, healthy fats and complex carbs" can be especially beneficial for women since it "can help balance hormones, boost fertility, and ease period problems."

Vitti's primary concern is for the nutritional needs of women in their reproductive years. She says, "It is also worth noting that historically women in their pre-menopausal years are left out of medical, fitness, and nutrition research." She says that whatever new recommendations arise from such research, they are touted in such a way that makes these women want to try the new diet or fitness plan, too, but they are inevitably disappointed when they "do not get the promised results."

Vitti notes the reason why results tend to vary for women is that they "have a second biological rhythm — called the Infradian Rhythm — which is only active during our reproductive years." She says that this rhythm, which coincides with the menstrual cycle, affects many of our bodily systems, including metabolism. Vitti says female metabolism has a "dynamic pattern," meaning that women's " calorie levels must change throughout the month." This is in contrast to the "static pattern" of male metabolism, which dictates that "their calorie levels must be the same each day."

According to Vitti, "eating for [women's] hormonal health requires shifting what we eat each week of [our] cycle[s] to support our body's shifting needs." To this end, she's developed her Cycle Syncing Method. To follow this plan, you "modulate [your] caloric intake based on the infradian rhythmic effect on your metabolic rate." In other words, eat less during the first half of your cycle when your metabolism's slower. Vitti says, "We need 279 more calories per day in the luteal [second] phase in order to keep blood sugar stable." You should also choose foods that help support the phases of your cycle; Vitti advises consuming "more amino acids in the menstrual phase to build more hormones for the next part of the cycle."

Cycle-syncing also affects exercise – Vitti says "in the first half of your cycle, resting cortisol levels are lower and in the second half they are higher," which means "you can do HIIT and cardio in the first half with excellent effect on lean muscle gain and fat loss," but should avoid these exercises during the second half since otherwise you could "lose lean muscle and store more fat."

Your cycle can even guide other activities, since according to Vitti, "the female brain changes up to 25 [percent] over the month and affords [women] different cognitive advantages like dialed-in verbal skills or super focus and concentration." If you can figure out your pattern, you can "reduce stress ... while working more efficiently."