If you and a friend both followed one of Muscle & Fitness Hers’ weight-loss plans to a T, you still might experience different degrees of success. Blame your parents: Research suggests that genes may play a significant role in determining how your body reacts to different dietary patterns. Unfortunately, finding the perfect diet for your DNA isn’t clear-cut. “Until science catches up with the average person’s ability to understand their personal predispositions, much of figuring out one’s best diet is trial and error,” notes Marjorie Nolan Cohn, R.D., a nutritionist based in New York City. Remember it’s not just your diet that affects weight and health—other variables such as sleep, exercise, toxins, and emotional stress also come into play.

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