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.
There are many ways to do intermittent fasting — ranging from fasting for a number of hours each day up to an entire 24-hour fasting period one or two times a week. “If you're trying to kick a habit like eating late into the night, then stopping eating earlier in the evening and fasting overnight could be beneficial for you,” says Hultin. “There are many types of intermittent fasting, so ensuring you pick one that works for you and your lifestyle is important.”
With its pre-packaged meals, portion-controlled menus, and strict caloric restrictions, the Nutrisystem meal delivery plan is ideal for people looking to lose weight fast without having to do any complicated meal planning. The company claims its 28-day program can help you lose up to 13 pounds by eating healthier versions of the foods you already love.
“The alkaline diet often has a focus on eating lots of fresh produce and unprocessed foods, which could be a good thing,” says Hultin. “However, keep in mind that this is not an evidence-based therapeutic diet. When people take it too far — for instance, drinking baking soda — or become too restrictive or obsessive over food choices, it can definitely turn negative.”
Right now, this is the trendiest of all diet theories. It prioritizes the consumption of foods high in protein and fat while limiting the number of carbs per day to less than 20%. This means abstaining from grains, starchy vegetables, and fruits, and filling up on protein and fat. The most famous of all low-carb plans is the Keto Diet, an approach based on the metabolic process of ketosis, which happens when you restrict your carb intake to less than 0.7 grams per day and your body starts using fat, and not carbs, as its main fuel. 
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.
After subscribing and placing your order, you’ll receive your weekly meal plan at home in a recyclable package. And, if you live in certain areas, you could also get your food at one of the company’s 200 local pick-up locations. One curious aspect of these locations is that most of them are located in fitness centers, so you can get your sweat on while picking your food. 
"Even though a smart diet is key, exercise can help boost your body's metabolism to shed fat. Through health care providers often recommend brisk walking or jogging, these exercises may not help you see the results you want. Instead, try interval training," shares Dr. Sean M. Wells, DPT, PT, OCS, ATC/L, CSCS Owner and PT, Naples Personal Training, LLC
Interested in following a more historical approach to eating? The Primal Blueprint is similar to the Paleo diet, which has roots in how our long-ago ancestors supposedly ate. This plan ditches grain, sugars, and processed foods while focusing on clean eating with plenty of protein (both animal- and plant-based), lots of vegetables, fruits, and healthy fats. The Primal Blueprint acknowledges other health factors too, advocating for lots of low-intensity activity, some high-intensity exercise, strength training, and plenty of sleep.
The number of calories you need to maintain or lose weight depends on a number of factors, including your age, sex, height, and level of physical activity, according to the FDA. To maintain a healthy body weight, the FDA recommends that you balance the number of calories you consume with the number of calories you burn through physical activity and your body’s metabolic processes. As a rule of thumb, the FDA recommends a standard 2,000 calorie diet for the average adult.
Make sure that the diet has been studied extensively for safety — and discuss any changes with your physician or registered dietitian before beginning a new diet. (If you don’t have a dietitian, find one in your area at the Academy of Nutrition and Dietetics website.) And do a self-check to ensure the diet fits with your own values and preferences.

"A study published in Nutrition Journal found that participants who ate foods high in monounsaturated fats for lunch (in this case, half an avocado) reported a 40 percent decreased desire to eat for hours afterward. Monounsaturated fats from sources like olive oil, nuts and avocados can reduce cholesterol, promote weight loss, even boost memory." — David Zinczenko, author of the Zero Belly Cookbook

U.S. News evaluated and ranked the 41 diets below with input from a panel of health experts. To be top-rated, a diet had to be relatively easy to follow, nutritious, safe, effective for weight loss and protective against diabetes and heart disease. The Mediterranean diet took the top spot, while the government-endorsed DASH diet, which stands for Dietary Approaches to Stop Hypertension, came in second.


“There are many diet plans on the market today that promote good health,” says Emily Kyle, RDN, who is in private practice in Rochester, New York. “The key is finding one that does not cause you stress or agony.” Ask yourself questions such as: Would the diet guidelines make you happy? Anxious? Stressed? Are you able to follow them long term? “Factors such as enjoyment, flexibility, and longevity should be strongly considered,” adds Kyle.
"Oolong, or 'black dragon,' is a kind of Chinese tea that's packed with catechins, nutrients that help promote weight loss by boosting your body's ability to metabolize fat. A study in the Chinese Journal of Integrative Medicine found that participants who regularly sipped oolong tea lost a pound a week, without doing anything else to change their diet or exercise habits." — Kelly Choi, author of The 7-Day Flat-Belly Tea Cleanse
Popularized by the documentary Forks Over Knives, the Ornish diet is a low-fat, plant-based diet plan based on whole grains, vegetables, fruits, and legumes. It's based on a lacto-ovo style of vegetarianism, allowing only egg whites and nonfat dairy products. It's packed with vitamins, fiber, and lots of filling plants to keep you satiated. Some studies have shown it can reverse heart disease and have beneficial effects on other chronic health conditions. (BTW, there is a difference between a vegan diet and a plant-based diet.)
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