To lose 40 pounds quickly, reduce calorie intake and increase exercise levels with the goal of shedding 1 to 2 pounds a week. Based on the assumption that 1 pound equals 3,500 calories, aim to lose 1 pound per week by attaining a calorie deficit of 500 calories per day. A calorie deficit is the difference between calories consumed and calories burned.
Experts at the Mayo Clinic suggest dieters exercise for at least 1 hour per day to lose weight quickly. Depending on the level of intensity, an hour of exercise can burn 100 calories or more.
Eat fewer calories
Decrease your food intake to between 1,050 and 1,200 calories for each day to reach a daily goal of a 500-calorie-per-day deficit.
Eat healthy foods
Eat a diet consisting of mainly vegetables, fish, fruit, lean meats and low-fat dairy options. Lower your consumption of fatty meats and dairy and foods high in starch or salt. Starchy and salty foods can increase your water retention, giving you added pounds of water weight.
Keep a food diary
For each day, keep a food journal recording both food and exercise. Recording your emotions can help you to understand how they might affect your eating habits or cravings for more unhealthy foods. If you understand the cause of food cravings, it's easier to eliminate them.
Follow effective dieting strategies
Some common dieting strategies include using a calorie counter, choosing smaller food portions and replacing high-calorie foods with low-calorie substitutes.