THURSDAY, April 2, 2020 (HealthDay News) -- While you're hunkered down waiting for the coronavirus to abate, you might get inspired to lose weight. But which diet is best?

The short answer is that all diets seem to work. The long answer is you'll probably regain the weight within a year.

"There is no diet that somehow magically helps you keep the weight off," said Dr. Gordon Guyatt of McMaster University in Ontario, Canada, who led a review of more than 100 studies that looked at diets.

Follow any diet you like, he said, and you'll take off some weight and lower your blood pressure and cholesterol levels. That reduces your risk for heart disease, including heart attack and stroke -- as long as you keep the weight off.

But that's easier said than done, Guyatt said, and as the numbers on the scale inch up, the benefits in terms of heart disease risk disappear.

"If nothing else, that takes a lot of willpower," he said. "I'm sure there are some people who did keep the weight off, but on average, it is very difficult. So, sorry, no magic bullet."

For the study, Guyatt's team looked at 121 published studies, which included nearly 22,000 people who followed popular diets or a control diet.

These diets included 14 low-carbohydrate and low-fat diets, such as Atkins, DASH (dietary approaches to stop hypertension) and the Mediterranean diet.

Both the DASH and Mediterranean diets are rich in fruits, vegetables and whole grains, nuts, legumes and fish, and low in sugar, fat and red meat. They are often touted as heart-healthy, but Guyatt said it's not clear that they have been proven to reduce the risk of heart disease and stroke.

Over six months, people who followed low-carb and low-fat diets lost an average of nine to 11 pounds, and their blood pressure also came down, the investigators found.

But none of the diets improved levels of "good" cholesterol (HDL-C) or lowered levels of C reactive protein, which is tied to heart disease, the study authors noted.

After a year, people on all diets studied had regained weight and lost any heart-health benefit. Those on the Mediterranean diet, however, did maintain a small benefit in cholesterol.

Based on these findings, you can expect the same initial weight loss on any of the diets -- so which one you choose is really a matter of personal preference, the researchers said.

According to Samantha Heller, a nutritionist at New York University Langone Health in New York City, "Diets, by today's standards, do not work. By work, I mean a sustainable lifestyle that promotes a healthy weight and meets the nutrient needs of the individual." Heller was not involved with the new study, but reviewed the findings.

Fad diets are temporary, often very restrictive and not realistic, she said.

"The environment in which we live does not promote healthy living, and it is difficult for many to resist the temptations of convenience and fast food," Heller added.

A more plant-based diet of home-cooked and less highly processed foods -- in other words a Mediterranean-type approach -- can help people lower their risk for chronic disease, manage weight and boost energy, she said.

"We need to buckle down and face the fact that a constant diet of fast, junk and prepared foods is not healthy," Heller stressed.

And, beware: You can gain weight eating anything -- even healthy food -- so portions as well as physical activity matter, she warned.

"We may get complacent over time, start snacking a bit more, having slightly larger portions of food, be less active," Heller said. "And, over time, these small changes can add up to slow, weight gain."

The report was published online April 1 in the BMJ.

More information

For more on losing weight, visit the U.S. Centers for Disease Control and Prevention.