"The 16:8 diet is where you eat for about eight hours of the day and then fast for the rest of the day," explains , PhD, RD, a senior dietitian at Ronald Reagan-UCLA Medical Center. Yep, thats a full 16 hours of no snacking or grazing whatsoever.
I know: Spending 16 hours a day without food ? Torture. But before you get too freaked out, know that most people generally plan their eight hours of feasting for between 10 a.m. and 6 p.m. So yeah, youre sleeping for a solid portion of the fast. (Whew.)
What exactly is the 16:8 diet?
Its pretty simple. Basically, during your 16-hour , you limit yourself to black tea, coffee, or diet soda. Then, for the next eight hours, you can eat whatever you want (no calorie counting needed). That's it.
Scientifically, at least, the 16:8 diet seems to check out. In a recent (albeit, small) study published in the journal , 23 obese men and women followed the 16:8 diet for 12 weeks. Compared to a group that had eaten normally, those on the 16:8 diet took in 350 fewer calories per day, lost a modest amount of weight (about 3 percent of their body weight on average), and lowered their blood pressure.
But, keep in mind: This was a small study and few others have examined the 16:8 diet specifically, so its tough to draw any firm conclusions just yet. More research needs to be conducted before we can see if and how it can be implemented into an actual plan effectively, confirms Beth Warren, RDN, founder of Beth Warren Nutrition and author of Secrets of a Kosher Girl.
Still, other types of intermittent fasting (and there are tons of different kinds) show promise. The , for example (eat normally five days a week, cut back to 20 percent of your normal daily calorie intake for the other two), resulted in more weight and fat loss compared to day-to-day calorie restriction in a 2017 study in the .
So, will I lose weight on the 16:8 diet?
In theory, yes. But its hard to really know how the diet might benefit a wide variety of people since most research on the topic involves people who are obese, not just those looking to shed a few pounds.
One potential benefit of the 16:8 diet? It can help if someone wants to lose weight because oftentimes overeating at night is a big factor in weight gain, says Warren. Fasting will take away that obstacle. In this sense, the timing of your eating window can impact how much weight you lose: Typically, time-restricted eating mimics the way we ate before 24-hour drive-thrus and fully-stocked refrigerators (read: no midnight snacks).
Sticking to an eight-hour eating window during daylight hours allows your metabolism to run as its supposed to-you fuel up for energy during the day (when youre most active), and stop eating for rest and recovery at night, per a 2017 article in the journal Nutrition Reviews .
Its also likely that fasting can put your body into a state of ketosis (without actually having to do the full-on keto diet), which means your body starts burning fat for energy instead of carbs, says Warren. After your body runs through its glucose and glycogen stores (a.k.a. sugars you burn for energy), it then turns to the next-available fuel source: fat, explains Hunnes.
Recent studies indicate that you might lose weight on this diet because when you fast, you are burning more fat for energy than you are carbohydrates, she explains. This fat-burning and the metabolic shifts that come with might increase your chances of losing weight. (Of course, the time it takes to enter ketosis varies based on the individual. , so your 16-hour fasting window might have you covered).
Are there any downsides to the 16:8 diet?
For starters, this diet (like literally any diet) might be hard to maintain. Say goodbye to dinner parties and late-night dates. And god forbid a friend is late to that 5 p.m. dinner you scheduled.
It may be sustainable if you stick to the strict regimen, Warren says. However, this is difficult to maintain in real-life scenarios like social functions.
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Beyond the downer of not being able to go out for a late-night fancy dinner, in rare cases the 16:8 diet could potentially lead to disordered eating, too, notes Hunnes. For example, if youre someone who doesnt do well with long periods of fasting, you might follow a 16-hour fast with a binge or even start to prolong fasting periods longer than you should. Both would be signs that the diets not working for you and that it could progress to something more serious like an eating disorder, she says.
If you eat too late, you could also potentially interfere with the quality of your sleep-so its best to eat earlier in the day, suggests Hunnes.
That said, two recent (once again, small) studies in Applied Physiology, Nutrition, and Metabolism show obese adults can stick to the 16:8 diet without developing or exacerbating body image issues, disordered eating patterns, or sleeping problems.
Should I try the 16:8 diet-and how do I start?
For a generally healthy person, there seems to be no harm in only eating for eight hours each day, says Hunnes.
And while more research is needed on the 16:8 diet, overall, could improve cholesterol levels and brain function, and lower your risk of developing heart disease, cancer, and stroke. Still, youre probably best off getting a clean bill of health from your doc before embarking on this diet, Hunnes notes.
So, how can you get started with the 16:8 diet? It might be wise to gradually ease into longer periods of fasting, says Hunnes. However, she points out, the long-term weight loss benefits from the 16:8 diet werent that much greater than those youd reap if you just ate less throughout the day or switched to a more plant-based diet-so you could try simply cutting back on how much youre eating or adding in more plant-based foods, too.
Its a personal choice, and everyone needs to make these choices based on their own lifestyles and ability, Hunnes says.
Some people who should not do the 16:8 diet? People with diabetes, kidney disease, or certain metabolic disorders. These conditions can alter your bodys balance, storage, and use of insulin and glucose, making the 16:8 diet a possibly unsafe choice, says Hunnes.
Another no-go? Pregnant and breastfeeding mamas. In short, youre eating for two, and youd be depriving you and your baby of essential food, nutrients, and much-needed energy when you need it.
Otherwise? If youre interested, give it a try. Just dont expect a miraculous slim-down and be prepared for 16 potentially hangry hours ahead.
The bottom line: The 16:8 diet may help with weight loss, but more research is needed to draw any solid conclusions.