If you're thin, even if you're out of shape, you're healthier than someone who's obese, right? Not necessarily! You could be TOFI. That's short for "Thin on the Outside, Fat on the Inside." In other words, you may look healthy, but you really aren't. The London Observer says that TOFI people often have an unhealthy, even dangerous buildup of fat around their organs. But since they're skinny, not even their doctors know they've got a problem without doing extensive tests!Basically, skinny TOFIs are plagued with visceral fat, which surrounds their organs, infiltrates their underused muscles, and wraps around their hearts. It's the same "bad" fat that can cause insulin resistance, diabetes, and heart disease. On the flip side, your basic overweight person has a lot of fat visible under the skin. But a lot of them are healthier than they look. Take Japanese sumo wrestlers. Even though they eat 5-thousand calories a day and are well into obese territory, they're actually pretty healthy. Most of them have low cholesterol, low insulin resistance, and low triglycerides - which contribute to hardening of the arteries. So how can you protect yourself from becoming a TOFI - "Thin Outside, Fat Inside"? First, invest in a pair of walking shoes and get moving! Exercise not only helps you lose weight, it also removes fat from your muscles, and helps keep more fat from being deposited. Then, get off the yo-yo diet cycle, which raises your risk of becoming TOFI. People lose weight starting at the top and bottom of their bodies, and the last fat to vanish is abdominal fat. And if you gain the weight back, you pack more of it around your mid-section, raising your risk for heat disease and other ailments.* And the final don't-be-a-TOFI tip: eat more grains and lentils. They help eliminate fat from your system and prevent visceral deposits from forming.Bottom line: If you get plenty of exercise, you'll be healthier whether you're skinny or not. And it'll help keep you from becoming a TOFI time bomb.