Toxins cause weight gain.
Credit: Larry Washburn / Getty Images

Bruce Blumberg
Developmental biologist at the University of California at Irvine

Background
Bruce Blumberg is on the trail of what he believes to be the missing piece of the obesity-epidemic puzzle: obesogens, or chemicals in food, packaging, personal-care products, furniture, paint, and hundreds of other common household items that interfere with our body's hormone production and cause weight gain.

Theory
Blumberg admits that no one knows just how big a role obesogens play in the obesity epidemic – "Is it one percent? Is it 90 percent?" – but his landmark work on one chemical compound suggests that toxins are worth worrying about in the obesity equation. Blumberg found that mice exposed to tributyltin (TBT), a chemical found in some vinyl, paint, wood finish, wood pulp, disposable diapers, and a slew of other products – and even the pups of mice exposed to TBT – get fat eating the same number of calories as their TBT-free peers. For obvious reasons, humans haven't been dosed in the lab, but two diabetes drugs, Actos and Avandia, activate the same fat-depositing gene as TBT and cause the same effect: weight gain. "How can you not connect the dots?" Blumberg asks. And TBT isn't the only troublesome toxin. Chemicals in colognes, moisturizers, and a range of other personal-care products, as well as those in Teflon and bags of microwavable popcorn, and the most insidious – bisphenol A (BPA) – all cause problems, he says. What this means, he adds, is that we're a population-wide experiment in progress.

Solution
Blumberg believes the FDA should ban chemicals like BPA outright. He's also involved in a "green chemistry" movement among scientists to develop safe chemicals for household and personal-care products. "The market will sweep out the obesogenic and endocrine-disrupting stuff because there will be alternatives," he says.