When obese people lose weight with behavioral therapy, their family members may get a bit trimmer as well, a new study suggests.

Cognitive-behavioral therapy (CBT) is one option for managing obesity, though it’s not widely available. It focuses on changing people’s thoughts and attitudes on eating and other lifestyle habits, and giving them practical ways to make improvements - like tracking their daily calories and keeping an “eating diary.”

In the new study, Italian researchers wanted to know whether the things obese patients learn in CBT might have a “ripple effect” in their families.

They surveyed family members of 149 obese patients going through the CBT program at the University of Bologna - which consisted of 12 to 15 weekly group meetings.

Six months after their relatives started the program, the study found, family members - mainly spouses and adult children - showed some changes for the better as well.

On average, they’d cut more than 200 calories from their daily intake at the study’s start. They were also eating a bit less fat and refined carbohydrates, and a bit more fruit.

It all translated into a weight loss of just over two pounds, on average. But the effects were bigger for the 35 relatives who were actually obese themselves.

They lost an average of six pounds, and seven of them lost enough to become officially “overweight” instead of obese.

“CBT in a family member might have a ripple effect (for) other family members,” senior researcher Dr. Giulio Marchesini told Reuters Health in an email.

One reason could be that family members decided to make positive changes to help the person who was in CBT - like ridding the kitchen of sugary, fatty temptations.

Even more likely, Marchesini said, is that the person in behavioral therapy instituted some healthy changes at home. A majority of the CBT patients - 101 of the 149 - were women, and were likely “in charge” of meal planning, Marchesini pointed out.

“I do not know how much this possibility might translate into different cultures,” he noted, “but this is definitely the case among Italian families.”

The study, published in the Journal of the American Dietetic Association, had its limitations. One was that the researchers tried to survey almost 500 family members of their patients, but got responses from fewer than half - 230.

So the responses might have come from the most motivated patients and supportive families, and might not reflect the reality for everyone who tries CBT for weight loss, according to Marchesini’s team.

In general, cognitive-behavioral therapy requires motivation, since it’s time-consuming and people have to commit to changing their outlook and behavior. And it’s not universally available, Marchesini noted. That’s true in the U.S., as well as Italy.

He argued that the potential effects on an obese patients’ family should be taken into consideration when thinking about the cost-effectiveness of CBT.

In the U.S., the cost of CBT varies depending on the specific program, but a typical figure would be between $100 and $200 per hour. Insurance may or may not cover it.

There’s some evidence that other weight-loss treatments can end up having effects on family members as well. In a small study out last month, surgeons at Stanford University found that obese relatives of patients who underwent obesity surgery lost weight in the year following the procedure.

The benefits were small. On average, obese family members (limited to those living with the patient) lost eight pounds.

The study included only 35 patients and 50 family members, and it doesn’t prove that weight-loss surgery for one person will benefit the whole family. But the researchers said it makes sense that it might, since obesity is a “family disease.”

Even when people have surgery to treat severe obesity, they have to commit to lifelong lifestyle changes afterward.

SOURCE: Journal of the American Dietetic Association, November 2011.