Commercial weight-loss programs: Evidence of benefits for diabetics still too scarce

"A few of these programs may be a viable option for improving blood sugar control in patients with type 2 diabetes and those at risk for the disease," says study leader Zoobia Chaudhry, M.B.B.S., M.D., assistant professor of medicine at the Johns Hopkins University School of Medicine, "but we need more gold-standard studies to make that claim."

Chaudhry says a wealth of previous research has shown that losing even a small amount of body weight -- between 5 and 10 percent -- can significantly lower blood sugar long term in people with type 2 diabetes, a condition long associated with being overweight and obese. But this research has mostly been based, she says, on intensive lifestyle interventions, including highly controlled diets and coached exercise, which aren't widely available to the nation's estimated 29.1 million people with type 2 diabetes.

In contrast, she adds, commercial weight loss programs, such as Weight Watchers, Jenny Craig and Nutrisystem (leading market share programs), are easy to access -- although at a price -- across the U.S. and in many other countries.

Though several studies have evaluated how much weight patients tend to lose through these programs, little was known about how they stack up in terms of glycemic benefits -- their positive effects on blood sugar concentrations. A high concentration is a hallmark of diabetes and can negatively affect long-term health, leading to a host of consequences, including blindness, kidney failure, nerve damage and cardiovascular disease.

To find out more, Chaudhry and her colleagues searched the medical literature for studies that carefully evaluated the effects of various commercial weight loss programs on blood sugar in overweight and obese individuals, including those with or without type 2 diabetes. They included only randomized clinical trials -- the gold standard for clinical research -- that lasted at least 12 weeks.

Their search, which is reported in the June issue of Obesity Reviews Journal, turned up only 18 studies that met their criteria, few of which focused specifically on individuals with diagnosed and documented type 2 diabetes. A total of 10 commercial weight loss programs were cited in the studies. Among the 764 people across all studies with type 2 diabetes, the Jenny Craig program reduced hemoglobin A1c -- a three-month average of blood sugar concentrations -- more than weight loss counseling alone at 12 months, and Nutrisystem and Optifast reduced hemoglobin A1c more than counseling alone at six months.

In 2,428 people without type 2 diabetes, few studies evaluated the effect of the programs on blood sugar. The six that did failed to show substantial reductions with any commercial weight loss program.

Chaudhry points out that it's possible that other commercial weight loss programs also have positive effects on blood sugar, both for people with type 2 diabetes and others at risk for this disease. However, she says, too few studies have rigorously evaluated glycemic effects for doctors to recommend commercial weight loss programs as a whole or any specific program to patients. Chaudhry hopes to investigate this further to uncover more definitive answers for patients and their doctors.

The U.S. Centers for Disease Control and Prevention has estimated that 29.1 million American adults have type 2 diabetes, of whom 8.1 million remain undiagnosed. Risk of this disease significantly increases with obesity, conditions that affect two-thirds of adults in the U.S. Recent studies have estimated that the cost of managing type 2 diabetes in the U.S. was associated with $245 billion in direct and indirect costs, and the costs of obesity and its associated conditions were estimated to be $147 billion. In 2014, the U.S. weight loss market's value was estimated to be about $60.5 billion, according to the Bharat Book Bureau, a market research information aggregator. Commercial weight loss programs often cost hundreds of dollars a month, and insurance companies typically don't pay for them.