There’s a reason a lot of us have a problem with slimming down (and keeping it off). Cutting-edge scientific studies are pointing toward a surprising new explanation??one which has little to do with lack of willpower. (Thank goodness.) Actually, the problem is that you’ve been doing what you were told to do??slash calories, cut fat.

Conventional wisdom holds that weight loss is nothing a lot more than simple math. Consume fewer calories than you expend, and also the pounds will fall off as predictably as leaves from an autumn tree. But thousands of failed diets have shown that the low-calorie approach fails, says David Ludwig, MD, an endocrinologist at Boston Children’s Hospital and a professor at Harvard Medical School. “When you cut calories, the body fights back, making you hungrier, amongst other things,” he explains. “Weight is controlled by our biology a lot more than our willpower.”

What’s more, despite everything you’ve probably heard for years, all calories aren’t created equal. “Although a bottle of cola and a number of nuts might have exactly the same quantity of calories, they’ve dramatically different effects on metabolism,” says Dr. Ludwig. (Bet you are able to guess that is worse.)

Three new books offer insights in to the latest thinking on smart eating, and they are all penned by eminent weight-loss experts: Dr. Ludwig; Louis Aronne, MD, director from the Comprehensive Weight loss Center at Weill Cornell Medicine and NewYork-Presbyterian Hospital; and Mark Hyman, MD, director from the Cleveland Clinic Center for Functional Medicine. Health chatted with these groundbreaking diet crusaders to uncover what we should all have to know to slim down and remain healthy permanently.

Once insulin ushers calories to your fat cells, it closes the door, restricting remarkable ability to leave. With calories, aka fuel, held in fat cells, there’s too little glucose and too few lipids circulating within the bloodstream to power your brain and muscles. Your brain, sensing the fuel shortage, prompts you to feel hungry and slows down your metabolism??the worst possible combination for long-term weight loss.

“Overeating hasn’t made our fat cells grow,” says Dr. Ludwig, whose book is titled Always Hungry?. “Processed carbs and added sugar have programmed our fat cells to develop, which causes us to be overeat.” Also it turns into a vicious circle. Break it: “If you’re going to have simple carbs, like bread with dinner, have them after you have eaten some protein and veggies first,” says Dr. Aronne. “Our studies show that when it will save you them later on within the meal, they don’t trigger as big a bump in blood sugar??or insulin.”

In a 2012 study published in JAMA, Dr. Ludwig and his colleagues looked at 21 people between the ages of 18 and 40 who were overweight or obese. They had each participant lose about 10 to 15 percent of their bodyweight, then put them on three different maintenance diets??low-fat (with about 60 percent of daily calories coming from carbs); low-glycemic-index (with about 40 percent of daily intake from carbs that create only moderate spikes in blood sugar, for example legumes and vegetables); and a very low-carb approach, with just 10 % of daily calories from carbs. The 3 diets involved exactly the same final amount of calories. And every participant tried each diet for any month.

After each diet period, they tested the folks’ metabolic rates??and found that the low-carb diet completely prevented the metabolic slowdown often seen after weight loss. “People on the low-carb diet burned an average of 325 more calories a day??comparable number you’d burn during a moderately vigorous workout??than those around the low-fat diet, and people around the low-glycemic diet burned 150 more calories compared to those on the low-fat diet,” he states. One theory for why that happens: Reducing processed carbs, and as a result insulin levels, allows fat cells to release calories back into the bloodstream, assisting to readjust the body-weight set point naturally, speculates Dr. Ludwig. He posits that reducing carbs even moderately??having a focus on the quality of your carbs??could be beneficial for reducing weight too.

One of the strongest studies vindicating fat was published in The New England Journal of Medicine several years ago. In it, researchers assigned 322 overweight people either to a low-fat diet, a moderate-fat Mediterranean diet or perhaps a low-carb, high-fat, high-protein diet. The trial lasted 2 yrs??a relative lifetime within the arena of diet studies. The things they discovered: Those on the low-carb, high-fat diet not only lost the most weight but additionally had probably the most favorable alterations in heart-disease-related factors, like amounts of triglycerides and HDL cholesterol.

For one thing, it shifts into conservation mode and just burns fewer calories, notes Dr. Aronne. In addition, he states, levels of hunger- and satiety-related hormones switch to increase your need to eat, causing you to feel less satisfied with an acceptable quantity of food and much more obsessed with high-calorie, packaged goodies. “It’s kind of like your brain goes haywire,” explains Dr. Aronne, “and you can no longer trust the messages it’s sending about hunger and fullness.”

But eating the right foods will help you minimize these biological defenses. The key: Consume a satisfying amount of protein, high-quality fat and fiber-rich, low-starch carbs from veggies, legumes, nuts, and seeds. “When you eat that kind of diet, insulin levels decrease and you reprogram fat cells to produce excess calories,” says Dr. Ludwig. “So there’s more glucose and lipids available as fuel??which means you’re not battling hunger as well as your metabolism stays high.”

To bolster these new dietary strategies, there’s some tried-and-true advice you should absolutely follow: Move more, sleep plenty, stress less??all of which will keep insulin levels, in addition to hunger and satiety hormones, at optimal levels, says Dr. Ludwig. Diet guidance may evolve, however these three fundamentals have stood the test of your time.

A.M. snack: 1 small container of plain Greek yogurt with ?? cup of blueberries.

From Dr. Aronne’s The Change Your Biology Diet ($26, amazon.com)

Snack: ?? cup of raw, organic nuts and seeds. For a greater nutritional punch, soak them in warm salt water overnight, rinse thoroughly, then dry in the oven at no more than 120 degrees.

From Dr. Hyman’s Eat Fat, Get Thin ($28, amazon.com)

Dessert: ?? medium pear, apple, peach or apricot poached with cinnamon, cardamom and ground nutmeg.

From Dr. Ludwig’s Always Hungry? ($28, amazon.com)