If you think losing a meaningful amount of weight is so monumentally difficult that hardly anyone succeeds, think again.

About 65 percent of patients lose 5 percent or more of their weight — enough to improve blood pressure and risk factors for diabetes — within six months of the tried-and-true approach of diet, exercise, and counseling, according to a review of obesity research published Wednesday in the New England Journal of Medicine.

The counseling piece is crucial — and should include at least 14 sessions over six months with a trained professional such as a dietitian or exercise specialist. That kind of hand-holding is readily available, the review said, not only at medical centers but through YMCA diabetes-prevention programs, commercial weight-loss plans such as Weight Watchers or Jenny Craig, and even through call centers that provide tailored guidance.

"With intensive counseling, patients get a lot of instruction, but, equally important, they get a lot of support," said psychologist Thomas Wadden, director of the Center for Weight and Eating Disorders at the University of Pennsylvania. "Partly, it's the accountability that makes the difference. If you're reviewing your progress every week with a counselor, you're going to try harder than if you're just recording your weight on a phone app."

For the paper, Wadden teamed with Steven B. Heymsfield, an obesity researcher at Louisiana State University, to sum up what is known about the causes of the obesity epidemic and how to battle it.

Some parts of their scholarly review come as no surprise.  Two-thirds of the U.S.  adult population is overweight (a Body Mass Index of 25 to 29.9) or obese (a BMI of 30 or more), a result of increasingly sedentary lifestyles and eating too much high-calorie food in super-size portions. The girth of the nation has led to soaring rates of diabetes, heart disease, and other chronic illnesses.

But less well-known is the fact that research has uncovered 11 uncommon genetic forms of obesity, including a type that is found in about 5 percent of severely obese children. Moreover, studies suggest that when fat people slim down, they continue to suffer metabolic and psychological effects such as increased appetite and a preoccupation with food.

"The implication is that persons who are no longer obese may not be physiologically identical to their counterparts who were never obese," the authors wrote.

If obesity permanently changes how the body functions, then that helps explain why so many who lose weight regain it. The authors say it also supports "the concept of obesity as a chronic disease that requires long-term vigilance and management."

Because of the chronic nature of the problem, professional guidelines recommend that anti-obesity medications be considered to supplement intensive counseling and lifestyle changes. Six drugs have been approved for short- or long-term use, and research by Wadden and others has shown that adding a medication leads to greater weight loss and better maintenance.

Nonetheless, studies suggest the medications are underused, given the scale of the obesity epidemic.

Wadden and his co-author cite the reasons: Diet drugs have a history of being barely effective or unsafe; insurance usually doesn't cover them; and patients are often disappointed that pills are no panacea — their losses are modest.

"It's clear that these medications are beneficial," said Wadden, who has been a paid consultant to pharmaceutical companies as well as Weight Watchers. "Unfortunately, there's a sense that they must not work if you have to take them indefinitely. But I think obesity medications should be used on a long-term basis for chronic weight management, just as I take a [cholesterol-lowering] statin and a blood-pressure medication for the long term."