According to its fervent proponents, humans were not made to be eating constantly; rather, we were designed to eat for short periods of time followed by hours (and sometimes days) of fasting. Much like vegetarianism, intermittent fasting is practiced for two main reasons: health and religion/spirituality. There are no food or caloric restrictions, but rather a restriction on WHEN to eat. The most popular methods include the 16/8 (8 hours of eating followed by 16 hours of fasting), the “Eat-Stop-Eat” method (two 24-hour fasts per week on non-consecutive days); and the 5/2 method (only 500 calories for 2 non-consecutive days, and 5 days of normal eating per week). While it's generally considered a healthy approach to eating when done moderately, some studies suggest extreme fasting may lead to hair loss and anxiety. 
If you like eating meat and want to lose weight, you might be tempted to try this recent extreme diet fad that proponents have made some pretty outrageous claims about. One: that eating nothing but meat can cure you of autoimmune diseases. The problem is that there’s no good research to support that notion, or any other health claim, for that matter. Indeed, omitting foods known to be good for you — fruits and veggies among them — can lead to a bunch of unwanted side effects, including constipation and potentially dangerous nutrient deficiencies. Still, since you’re cutting out so many food groups, there’s a decent chance you’ll lose weight, experts say. Regardless of any possible benefits you might see, this restrictive approach is definitely one you’ll want to ask your doc about before you even consider diving in.

To prep his patients for success, Dr. Seltzer tells them to plan around a large evening meal by eating a lighter breakfast and lunch—NBD since most people who eat a meal before bed tend to wake up feeling relatively full, he says. Research suggests balanced bedtime meals may also promote steady next-day blood sugar levels, which also helps with appetite regulation.
The "all meat all the time" low-carb approach or strict veganism can be great options for people who thrive on clear diet rules (and those two are actually the most popular diets out there) but these extremes are not for everyone. If you prefer more of a moderate approach, the Flexitarian diet is the clear winner. The "flexible vegetarian" mindset allows you a healthy balance of plant-based foods, responsibly sourced meats, and quality fats. The best part? It's not super restrictive, so you have plenty of nutritious food options. (Start here: How to Adopt a Flexitarian Diet)
"Anytime you’re stressed, you probably go for food," Dr. Seltzer says. (Have we met?!) That’s because cortisol, the stress hormone, stokes your appetite for sugary, fatty foods. No wonder it’s associated with higher body weight, according to a 2007 Obesity study that quantified chronic stress exposure by looking at cortisol concentrations in more than 2,000 adults’ hair.
If you want to lose weight fast, your best bet is the HMR Program, according to the health experts who rated the diets below for U.S. News. While these diets enable quick weight loss for those with a short-term goal – there's a strong chance you'll drop significant weight within the first 12 months – keep in mind that this is markedly different from long-term weight loss, which is more important for your health.

If you don’t have an established exercise routine, “walking is a pretty good entry point for people,” says Gagliardi. One small study published in The Journal of Exercise Nutrition & Biochemistry found that obese women who did a walking program for 50-70 minutes three days per week for 12 weeks significantly slashed their visceral fat compared to a sedentary control group.
Weight loss ultimately comes back to the concept of calories in, calories out: Eat less than you burn and you’ll lose weight. And while it’s possible to lose water weight quickly on a low-carb diet, I certainly wouldn’t advocate for it. The diet itself can trick you into thinking that this eating style is working — when really, you might gain back what you lost as soon as you eat carbs again. That can feel incredibly dispiriting if you want results that last longer than a week.
Based on the concept of caloric density, which states that some foods have few calories in proportion to their size (say, a lettuce), while others have lots of calories packed in small portions (a regular chocolate chip cookie comes to mind), Volumetrics divides foods into 4 categories based on their calorie/volume ratio, and is perfect for people looking to binge on some foods while still shedding pounds. However, as with the calorie counting approach, Volumetrics does not take into account the quality of the calories, prioritizing quantity instead. The app Noom and Weight Watchers (both reviewed above) share similarities with this diet theory.
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