Rather than losing more pounds, you may be struggling to gain weight rather than losing more pounds. Increase calories by 250-500 calories per day. To your regular calorie intake, try an extra snack or small meal. Although a few hundred calories may not seem to be much, you’ll gain about a pound a week, which is a healthy increase. Being underweight can be just as harmful as being overweight, so keeping a BMI between 18 and 18 is important. 9 improves overall wellbeing. If this number differs, don’t be concerned because your fitness level and genetic makeup may cause you to gain or lose a little bit.