always hungry book Dr. David Ludwig

We've been told a lot of things about diets over the years.

Fat is bad for you. Everyone should get six to 11 servings of carbohydrates per day. Burn more calories than you eat, and you can lose weight.

But it turns out that many of these recommendations don't line up with decades of published research on nutrition.

Dr. David Ludwig, a Harvard Medical School nutrition and obesity expert, has a diet plan outlined in his new book, "Always Hungry? Conquer Cravings, Retrain Your Fat Cells, and Lose Weight Permanently."

And it is among the most sensible, scientifically supported diets we've ever seen.

What you do

The program starts with a two-week boot camp designed to stamp out cravings. You completely cut all grains, processed sugars, starchy vegetables, alcoholic beverages, and artificial sweeteners from your diet.

Legumes, non-starchy vegetables, and whole fruits (up to three a day) are allowed. Every meal should include a serving of protein (like meat, eggs, cheese, and Greek yogurt) and fat (like olive oil, avocado, and nuts). About half of your calories come from fat during this phase.

Over phases II and III, you gradually add grains back in, but try to focus on whole, unprocessed ones like quinoa and oats. Phase II allows starchy vegetables (like squash), but still forbids white potatoes. By Phase III, the rules are very loose, but everyone is encouraged to find the amount of carbs and sugar that can be "tolerated": if you find yourself with insatiable hunger or cravings again, it's time to cut back.

By the end of the program, about 40% of calories should come from fat, while 40% come from carbs, and 20% come from protein.

no carb low carb diet pork chop avocados food The kind of meal you can eat on Ludwig's Always Hungry plan: pork chop cooked in olive oil with avocado atop a salad tossed with full-fat vinaigrette. dabinsi/Flickr

Why it works

Ludwig's "alternative hypothesis" for why his plan works is somewhat controversial in the field, and some mainstream endocrinologists we talked to say it's based on conjecture rather than hard science.

But he put together the plan citing his own extensive research (some of which can be found here, here, here, and here) as well as many other studies examining why we gain and lose weight. 

Ludwig explained to Tech Insider his hypothesis, which he's been testing for years: 

When we eat processed carbohydrates, like white bread or cookies, the insulin levels in our body skyrocket. That much is not contested.

But Ludwig goes further. His idea is that this spike in insulin makes our fat cells suck up calories and hold on to them. With so many calories being stored in fat cells, the amount of calories in the blood are lower, so the brain thinks that the body is hungry. 

And one of the fastest ways to get more calories in the blood is to eat more simple, processed carbohydrates. So we eat them — and then we crave more.

It's a vicious cycle, Ludwig says, that can lead to a slowed metabolism, and eventually obesity. (Ludwig's research is also part of what's behind similar diets like the South Beach Diet.)

He explains that the purpose of the diet's first phase is to "retrain our fat cells" to release the calories they're storing so the body can recognize when it's actually hungry again. Ludwig says this retraining occurs when you predominantly replace processed carbohydrates and added sugars with high-fat, whole foods. 

"You lower insulin [and] calm chronic inflammation, so fat cells stop taking up so many calories and there are more for the rest of the body," Ludwig says. "Hunger naturally declines, metabolism speeds up, and you start losing weight with your body’s cooperation, not with your body kicking and screaming." 

What the science says

Putting aside Ludwig's contested explanation for why it works, the "Always Hungry" plan recommendations themselves line up with decades of sound research on diets.

Scientific reviews have concluded: that low-fat diets are less effective than high-fat or low-carb diets; that sticking to a diet is the most important part of any plan; that cutting calories isn't sustainable; and that consuming too much added sugar can contribute to weight gain, cardiovascular disease, and type 2 diabetes.

Ludwig insists — citing results from the pilot study testing the plan — that participants truly don't crave processed carbohydrates or sugars in the same way once they reach phase III, so it doesn't feel like you're depriving yourself of food you want. It's sustainable.

Old Couple Walking Ludwig recommends taking a stroll after dinner, a practice the Italians call, "passeggiata." Flickr / Francisco Osorio

That's also partially because participants don't count calories, and can eat when they're hungry.

Beyond the eating plan, Ludwig makes additional recommendations that are firmly grounded in weight-loss research, including getting enough sleep, keeping stress levels at bay, and adding enjoyable activities so you'll actually want to exercise.

It's truly a lifestyle plan — and one that is designed for lasting change. Participants should feel satiated by Phase III, such that they can continue indefinitely and avoid the yo-yo effect often sparked by the constant hunger that accompanies many diets.

As Ludwig continues gathering data on people following the plan, he might be able to convince the skeptics that he's right. But as with much in the world of nutrition and health, we often know that things work before we know why they do.

The mantra of the program is: "Forget calories, focus on the quality of the food, and let your body do the rest." That sounds like good advice to us.