When attempting to get that beach body for the summer, many people turn to fad diets, crazy exercise plans, and incredibly complicated calorie-cutting methods. What most people don’t know is that the key to weight loss is much less complex; if you want to lose weight, all you have to do is start eating “green.”

According to Dr. Charles T. Nguyen, co-author of The Thinsulin Program: The Breakthrough Solution to Help You Lose Weight And Stay Thin, the No.1 culprit in weight gain and obesity is your insulin levels. High insulin levels cause the body to store fat, whereas low insulin levels cause it to burn fat.

So how can we keep our insulin levels low?

“If you eat green, leafy vegetables, the pancreas doesn’t need to produce insulin, so the insulin levels are lowered, because there’s no fat and no carbs, in these foods,” Nguyen told Newsmax Health.

Vegetables like asparagus, bok choy, spinach, kale, and arugula are prime examples of what Dr. Nguyen calls “green-light foods,” or foods that will lower a person’s insulin levels, and increase weight loss.

Of course, eating only vegetables would make for a pretty boring diet. Acknowledging this, Dr. Nguyen mentioned a few “yellow-light foods,” which could raise insulin levels if not portioned correctly. These foods include fruits and nuts.

“In some fad diets, like the Paleo diet, fruits are not allowed, said Nguyen. "This is wrong,” he continued, saying that “fruit will not spike insulin levels as long as you eat the right amount. The Thinsulin program recommends fruits like apples, oranges, grapes, and any kind of berries.”

Proteins, too, are a good choice for keeping insulin levels low, especially those found in meats and egg whites.

On the flip side, one should avoid eating sweets and starchy vegetables, like potatoes, corn, carrots, and beets, as these foods will spike insulin levels. “Any type of grain will raise the insulin levels, causing weight gain, regardless of how ‘healthy’ they may be,” he said.

It is for that reason that Dr. Nguyen recommends people stay away from beer, because it is made from wheat, which spikes insulin levels. “Have you ever seen a wine belly? That’s because wine is made from grapes, a fruit that will keep insulin levels low,” he explained.

“In order to beat this cycle of obesity, to really change it, we have to reject this idea of dieting,” Dr. Nguyen said, noting that a diet is usually associated with “punishing oneself, and then rewarding oneself for trying.”

“People looking to lose weight should look at it as a journey. In this way, people want to lose the weight, and understand that there will be little bumps in the road, but that they’re still getting where they want to go.”