First, the bad news: Three-quarters of Americans have a "fat gene" associated with a 20 to 30 percent higher risk for obesity. But that doesn't mean you're destined to be heavy. For starters, research found that just believing that you have the fat gene may actually reinforce unhealthy behaviors. Plus, a British review found that exercise can trump your genetics: Physically active people with the fat gene are 27 percent less likely to become obese than couch potatoes who have it. We're not talking about training for a triathlon; the active people got just one hour or more of moderate-to-vigorous exercise a week. Aim for the recommended five hours a week (three days of cardio and two days of strength training) and you'll rev your weight-loss results even more.
Weight can affect a person's self-esteem. Excess weight is highly visible and evokes some powerful reactions, however unfairly, from other people and from the people who carry the excess weight. The amount of weight loss needed to improve your health may be much less than you wish to lose, when you consider how you evaluate your weight. Research has shown that your health can be greatly improved by a loss of 5–10 percent of your starting weight. That doesn't mean you have to stop there, but it does mean that an initial goal of losing 5–10 percent of your starting weight is both realistic and valuable.
The most controversial part of this diet is the severe fat restriction. The American Heart Association recommends a diet with 25% to 35% of your calories from fat. The Pritikin Principle requires you consume less than 10% of your calories from fat. Besides providing taste to your diet, dietary fat has other functions, and 10% may be too low to meet your needs. There has been a considerable amount of research showing the health benefits of omega-3 fats, including protecting your heart. The American Heart Association now recommends that people without coronary heart disease eat a variety of omega-3 fat-containing fish at least twice a week and that those with coronary heart disease consume one gram of omega-3 fats per day. Dietary fat is also needed to transport the fat-soluble vitamins A, D, E, and K. Without fat to transport them, they will not be able to serve their functions in your body.
The conclusion? A caloric deficit is the sole cause of fat loss. Even if those calories come from the shittiest sources known to mankind, fat will STILL be lost. It’s not the source or the quality of those foods and the calories they provide… it’s the total quantity of it all. (Additional details here: Is Sugar Bad For You? How Much Should You Eat A Day?)