Scouts were required to have a physical exam prior to the annual fitness competition in West Virginia and anyone with a BMI of 40 or more is prevented from attending the gathering, FoxNews.com reported Monday.
Anyone with BMIs between 32 and 39.9 must provided additional health information to participate.
Patricia Bannon, a registered dietitian and author of "Eat Right When Time is Tight" said the ban is meant to protect scouts who could become ill during the 10-day competition, which includes scaling a mountain, but said the boys shouldn't be banned.
"Unfortunately it still does exclude children due to their weight, but I'm sure they're looking at their health and potential negative health consequences," she said. "But maybe they could walk [the course] or do what they can and not be excluded. Anything that the Boy Scouts could do to compensate for the stigma of being excluded would be great."
The Council on Size & Weight Discrimination said the policy was "unfair" and "discriminatory."
"There are boy scouts who are heavier than average but extremely fit and capable of strenuous physical activity. At the same time, it is patently absurd to assume that just because a boy is thin, that means he is capable of a three-mile hike up a mountain," the group said in a statement.