A Dietary Halo Effect That Can Be Very Real

Food marketers know how to use a dietary health halo. The marketers of California walnuts, for example, are polishing a halo for their brand with great skill. Eat more! They’re good for you! You might even lose weight! In that context, a health halo is all about a little science and a lot of wishful thinking. However, a different kind of healthy halo might have some merit. A prospective study in the International Journal of Obesity (IJO) suggests that a dietary program for one member of a family might have a halo effect on other members of the family.

A Mediterranean Diet for Weight Loss

This is a secondary analysis of data from the PREDIMED-Plus trial. That trial was a six-year RCT of a Mediterranean diet and physical activity program for weight loss and prevention of cardiovascular events. But this study looked at changes in weight, diet, and exercise for family members of subjects in the trial. Those family members didn’t get the treatment the PREDIMED-Plus subjects did. They just lived with them.

So researchers wanted to see if any of the benefits of lifestyle treatment would rub off on family members. It’s a reasonable question because the lifestyle of one family member can easily influence others.

Indeed, these researchers did see a dietary halo effect. After two years, family members in the treatment group had changed their diets more than family members from the control group. Also, they lost more weight – an extra four kilos.

But the halo effect did not extend to physical activity.

Health Can Be Contagious

This is the first prospective study of a contagion effect for a diet and exercise program to reduce weight. But other researchers have found evidence for a family benefit in weight management and in dietary changes. In the Look AHEAD trial, untreated spouses of subjects in the intensive lifestyle group lost more weight than spouses of subjects in the control group. Gastric bypass and sleeve procedures may lead to weight loss in close family members.

On the flip side, we know that a contagion effect for obesity is a real thing. It spreads in social networks. Put that fact together with a halo effect for dietary changes and weight loss, and it makes sense to expect a prevention benefit from obesity treatment.

Perhaps if we offer good obesity care to people who are most affected, treatment might have some effect on interrupting the spread of obesity in social networks. Food for thought.

Click here for the study in IJO, and here for more on the close relationship between obesity treatment and disease prevention.

The Angel of Revelation; painting by William Blake / WikiArt

Subscribe by email to follow the accumulating evidence and observations that shape our view of health, obesity, and policy.

March 22, 2021