Although two-thirds of Americans are overweight or obese, a handful of skinny people—including many athletes—feel frustrated by their seeming inability to gain weight. Clearly, one’s genetics play a powerful role in this. “Hard gainers” also tend to be fidgety and see their attempts to gain weight thwarted by non-exercise activity thermogenesis, the technical term for spontaneous movements that naturally occur in fidgety people. And while you can’t change your genes or your tendency to fidget, there are steps you can take to bulk up. Start by eating consistently—skipping meals means you will miss out on important calories. And eat larger than normal portions if you can, selecting higher-calorie foods where possible. I also recommend drinking lots of 100-percent fruit juice and low-fat chocolate milk. Quenching your thirst with milk rather than water easily adds 300 to 600 wholesome calories a day to your diet. Similarly, adding peanut butter, nuts, avocado, and olive oil to your diet will boost your calorie count with good fats. Finally, try mixing strengthening exercises in with your cardio. Weight lifting and push-ups stimulate muscle growth so that you bulk-up instead of fatten up. Plus, exercise stimulates your appetite and, sooner or later, you’ll want to eat more.