There are several issues to address in your question. As to your diet, it’s important that you eat more than once a day. Eating so infrequently on a regular basis will sabotage your metabolism and cause spikes in blood sugar and insulin – which will lead to weight gain. Plan your shopping and food preparation ahead of time, so that you’re never caught without a good source of food, and force yourself to eat more frequently. If you’re not hungry, realize that even a small meal portion will help keep your metabolism stoked.
Focus on quality, whole foods. Choosing the right foods will not only make you leaner (and stronger), but they will reduce your risks of cancer, heart disease, stroke, and diabetes. With every meal opportunity, attempt to get a good source of protein with lots of vegetables. Good fats are important too – nuts, avocados, fatty fish, olive oil, coconut oil, etc. Avoid sugar, refined carbohydrates, soft drinks, vegetable oils and processed foods.
Finally, it’s not necessary to join a gym to get into shape and lean out, nor do you have to start running marathons or long distances. If you run, try running faster for shorter distances – quality is more important than quantity. Try some interval training and keep your sessions limited to 15-20 minutes, focusing on intensity. Balance 3 of these higher intensity workouts with some alternate activities that you enjoy – cycling, playing a sport, hiking, swimming, etc throughout the week.
I highly recommend lifting some weights, as there is no better way to increase insulin sensitivity and your metabolic rate. Weight training will not cause you to “bulk up”; women simply don’t have the testosterone levels to enable hypertrophy. You should be doing functional, multi-joint exercises that use various muscle groups – think of moves that incorporate pulling, pushing, and those that involve the hips, core and lower body. If you don’t have access to weights, you can still do pushups, body rows, sit-ups, squats and many other body-weight exercises.
Response by Greg Carver