“What diet should I follow to lose weight?” As a health and exercise professional, you’ve undoubtedly been asked some variation of this question a thousand times. A new review of the literature on diets and weight loss offers insight on what the best answer you can give your clients might be.

Researchers examined the latest scientific evidence on a variety of diets, commercial diet plans such as Weight Watchers, exercise, obesity medications and different types of bariatric surgery. Based on this review of more than 400 studies and peer-reviewed articles on obesity, they concluded that low-carb, low-fat and other diet plans all are capable of helping some people achieve modest long-term weight loss with potential improvement in health risks. The key word here is “some,” meaning that no single diet proved to be most effective for everyone. However, the Mediterranean diet and Dietary Approaches to Stop Hypertension (DASH) eating plan also offer demonstrated benefits for improving cardiovascular health, and in lower-calorie versions may also be beneficial for weight loss.

So, while researchers concluded that most diets will work for some people, they also highlighted the fact that all of the weight-loss interventions had a high degree of variability when it came to effectiveness.

“Individual weight-loss approaches worked well for some people and not for others,” says George A. Bray, M.D., of Louisiana State University’s Pennington Biomedical Research Center in Baton Rouge, La., who chaired the task force that developed the report. “Currently, we have limited genetic and other information to predict which intervention will work for a given individual. This demonstrates just how complex the problem of severe obesity is.”

Additionally, many consumers turn to dietary supplements, which are not evaluated by the U.S. Food and Drug Administration (FDA). There is little scientific evidence to show these supplements can effectively support weight loss or even that they are safe. Having the FDA oversee dietary supplements and holding these products to higher safety and efficacy standards would benefit public health, according to the researchers.

Recent studies have examined whether some individuals with a body mass index (BMI) that meets the criteria for obesity can maintain healthy blood pressure, cholesterol levels, blood sugar and levels of fats called triglycerides in the blood. The researchers believe that metabolically healthy obesity is likely a short-term state, and individuals who fit the criteria are likely to develop metabolic and cardiovascular problems over time.

Given the number of diets, medications and surgical procedures available to treat obesity, the best approach for each individual depends on genetics, health and how well they can adhere to a particular regimen, the researchers concluded. Still, maintaining long-term weight loss remains challenging, and individuals with obesity should expect to regain weight when they stop treatment.

“The stigma around this disease makes it difficult to address obesity as a public health problem,” says Bray. “There often is a mismatch between the patient’s cosmetic goals and what can realistically be achieved with diet and exercise. While a modest 5 to 10% weight loss can yield significant health benefits, that may not provide the cosmetic changes patients seek.”

What This Research Means to Health and Exercise Professionals

Obesity remains a worldwide public health issue. More than 1.9 billion adults worldwide meet the criteria for obesity or overweight, according to the World Health Organization. It is associated with, and contributes to, a shortened life span, type 2 diabetes, cardiovascular disease, some cancers, kidney disease, sleep apnea, osteoarthritis and other conditions. Weight loss can lower the risk of developing these conditions and improve health outcomes. As a health and exercise professional, you are well positioned to provide the guidance individuals need to lose weight and, ultimately, reduce their risk of these diseases and improve their overall health and quality of life.

While your ultimate goal is to help your clients achieve permanent lifestyle change, helping clients who struggle with obesity lose as little as 5% of their body weight can go a long way toward improving their health and well-being. For this reason, the best answer to the question of which “diet” is best for weight loss is the one that an individual will be able to stick to and follow.

“Effectively treating obesity is crucial if we are going to be able to address the devastating impact diabetes and cardiovascular disease have on public health,” Bray says. “As our scientific understanding of obesity continues to improve, we hope this will lead to the discovery of new treatment approaches.”