You can safely lose 1 to 2 pounds per week, according to WebMD, so it can take around 20 weeks to lose 40 pounds. You need a food scale and methods of tracking your intake and physical activity.
- Determine your calorie intake needs
Use a calorie-needs calculator to see how many calories you need per day to maintain your weight. Losing 1 pound requires a 3,500-calorie deficit, so once you have your maintenance calorie number, subtract 500 from your daily quota to lose 1 pound per week.
- Weigh everything you eat
Weigh all your ingredients whenever you cook. This includes vegetables, meats, oils and sauces. Use a food scale instead of volume measurements, and weigh foods when raw for a more accurate result.
- Track your calories
Track the foods in a food journal. There are free online options for this, but you can easily do this with a physical notebook. Try to stay near your daily calorie goal in order to see quick results.
Add physical activity to your life and track how many calories you burn. According to the American Heart Association, simply walking or biking daily can burn 250 to 500 calories, depending on your weight and intensity. Burning extra calories supplements your reduced intake, so you lose weight more quickly.