We’ve all been told that eating too much combined with little physical activity is a recipe for weight gain. Now there is an opposing theory to this century-old belief. It’s processed sugars and carbohydrates that are the real culprits in obesity, not overeating, a recently-published commentary says.

More than 40 percent of American adults are obese, according to the Centers for Disease Control and Prevention, putting over 150 million people at greater risk for heart disease, type 2 diabetes, stroke and some forms of cancer. Clearly, obesity is a problem that needs a solution.

Diets have changed. Our great-grandparents’ meals consisted primarily of crops and animals that they worked hard to raise. Today we are inundated by high calorie processed foods that are cheap to produce, quick to fix, and created to taste really good.

The Dietary Guidelines for Americans, put out by the USDA every five years, is a source of official government guidance on nutrition. The guidelines advise adults to “reduce the number of calories they get from foods and beverages and increase the amount expended through physical activity” to lose weight. This approach is known in nutrition circles as the energy-balance model.

Food and diets have changed since our grandparents’ or great-grandparents’ meals consisted primarily of crops and animals that they worked hard to raise. Today we are inundated by high-calorie, ultra-processed foods that are cheap to produce, quick to fix, created to taste really good, and heavily marketed to people beginning in toddlerhood. Few people work hard enough to burn through the calories they consume in a day’s time. This should explain the obesity pandemic, right?

Not so fast. Public health messages have encouraged people to eat less and exercise more for decades, and people have tried it with little long-lasting success. Yet the problem of obesity and obesity-related diseases has only gotten worse.

Replacing the Energy-Balance Model

Seventeen internationally-recognized scientists, clinical researchers and public health experts decided to share what they believe is the real cause of obesity from a biological perspective, and it has nothing to do with overeating and lack of exercise. As they lay out in their commentary, they believe what is called the carbohydrate-insulin model offers a better explanation for weight gain than the 100-year-old energy-balance model, and it could be the basis for creating more effective and long-lasting strategies for managing weight.

The carbohydrate-insulin model places the blame for the obesity pandemic squarely on our modern diets. Simply put, we eat too many processed carbohydrates that digest very quickly causing hormonal changes that lead to weight gain.

When you eat foods containing highly processed carbohydrates, it forces the body to produce more insulin, a hormone needed to metabolize sugar. This triggers other hormonal changes that signal the body to conserve energy or calories and to store more calories as fat. Your metabolism slows down. The "conserve energy" signals cause feelings of hunger to arise. So we eat more.

This is not a low-carb diet. This is a low-processed carb diet. There’s a difference.

Eating less of the highly processed, quickly digested carbohydrates reduces the body’s drive to store calories as fat. And that, researchers believe, is the key that could unlock the secret to weight loss.

Though these are the beliefs and opinions of 17 acclaimed nutrition and public health experts, solid research is needed to test the energy-balance model against the carbohydrate-insulin model of weight gain. The authors call for more research to settle the debate.

In the meantime, if you’ve been unsuccessful at losing weight you can do your own weight loss experiment. Try cutting back on calories from processed foods and increasing your activity. Eliminate foods made with white flour such as bread, tortillas, bagels, biscuits, waffles, pastas, pastries, and pizza made with white flour crusts. Avoid highly processed breakfast cereals, cookies, cakes and doughnuts. Granola, sodas, fruit drinks, yogurt, pasta sauce, ketchup and barbecue sauce are other, often hidden, sources of refined sugars.

Instead, shop for foods made with whole grains and little or no refined sugar. These foods generally contain fiber which takes longer to digest and helps you feel full longer. You just have to take the time to read food labels until you get the hang of it. Then eat reasonable portions, and see if it makes the scale move in the opposite direction.

Here’s what you need to keep in mind: This is not a low-carb diet. This is a low-processed carb diet. There’s a difference.

The study is published in The American Journal of Clinical Nutrition.