 Obesity is so rare among those eating plant-based diets, nutrition researchers have been desperate to uncover their secret. Yes, they tend to eat fewer calories, but not that many fewer. In the past, I've gone through a couple of theories that have emerged. Maybe it's because people eating plant-strong diets express more of the fat-shoveling enzyme inside the power plants, the mitochondria within their cells. Maybe it's because they grow different populations of good bacteria in their gut. Maybe it's because they're avoiding the obesogenic endocrine disrupting the industrial pollutants in the meat supply. An obesity-causing virus in poultry may even be contributing. We're still not sure, but the theories keep coming. Here's the latest. Maybe it's to propionate. After all, what's one of the things that's only in plant foods and never in animal foods? Fiber. Animals have bones to hold them up. Plants have fiber to hold them up. I thought fiber was defined, though, by our inability to digest it. Sure, we can't break it down, but the gazillions of good bacteria in our guts can. What do they make with it? Propionate, which gets absorbed into our bloodstream. So technically, we can digest fiber, but just not without a little help from our little friends. What does propionate do? Well, it inhibits cholesterol synthesis. That's nice. It also appears to have a hypophagic effect, meaning it helps us eat less, apparently by slowing down the rate at which food empties from our stomachs, thereby making us feel fuller longer. Propionate may either regulate food intake, or the generation of new fat cells, resulting in an overall anti-obesity effect. One of the many ways fiber-containing foods, meaning whole plant foods, can help us control our weight.