Losing any amount of weight requires you to burn more calories than you consume. Since 1 lb. equals 3,500 calories, for 20 lbs. you must create a 70,000 calorie deficit over several weeks. The most successful rate of weight loss is 1 or 2 lbs. per week says Joanne Larsen, R.D. on Ask the Dietitian, meaning with the right foods and strategies, you could lose 20 lbs. in just about 10 weeks.
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Significance of Calories
Calories are what matter for weight loss, not the particular combinations or macronutrient ratios. A study published in the "New England Journal of Medicine" in February 2009 compared four different diet plans with disparate amounts of fat, carbohydrates and proteins. The Harvard researchers concluded that it was ultimately the low-calorie nature of the diets that yielded loss, not the food combinations. Eat fewer calories than you use, and you will lose your 20 lbs. Do not go below 1,200 calories a day as a woman or 1,500 as a man warns MedLine Plus website.
You could technically lose weight by ingesting donuts and French fries all day as long as you ate below your daily burn rate. However, your serving sizes would be exceptionally small to fit your calorie target. In addition, you would experience nutritional deficiencies, lose muscle mass and put yourself at risk for healthy problems related to too much saturated fat and sugar. A better strategy is to emphasize balanced meals that include reasonable portions of healthy foods most of the time. This supplies you with adequate nutrition for growth and energy, as well as allows you to eat large enough servings to not feel deprived and frustrated while dieting.
Types of Foods
To lose 20 lbs. at a rate of 1 or 1 lbs. per week, emphasize whole foods with a low calorie density. Build your meals around watery, green vegetables which offer nutrition and fiber, but not a lot of calories per serving. You can eat 3 cups of raw spinach for just 15 calories, while a small order of fries from McDonalds costs you 230 calories. Choose lean proteins--fish, skinless turkey or chicken breast, shrimp or very lean beef--and eat just two to three, 3 oz. portions daily. Measure out ½ cup servings of grains--or one slice of bread--at each of your meals and snacks and go for whole varieties as much as possible--choosing brown rice over white, whole wheat bread over white and oatmeal instead of puffed rice. If you want to lose your 20 lbs. quickly, you do not have a lot of room for discretionary calories that come from saturated fats that include butter and fatty meats, sugars from sodas or candy or alcohol.
Many people think that fat is the enemy when they are trying to lose weight. The body needs fat to pad the internal organs, regulate hormone production, keep the hair and skin healthy and absorb specific vitamins. All fats are not optimal for your health or weight loss goals. A diet to lose 20 lbs. will emphasize unsaturated fats--such as the ones found in olive and canola oil, avocados, fatty fish, nuts and seeds. Shoot for 25 percent to 35 percent of your daily calories to come from these healthy sources, and avoid saturated fats and cut out trans fats--found in processed foods--altogether, advises the American Heart Association.
Although you can lose weight by dieting alone, you will probably have more success combining the right kinds of foods with exercise. Eighty-nine percent of the National Weight Control registry members--an ongoing research group of successful losers who have kept an average of 66 lbs. off for over five years--used diet and exercise to achieve their goals. Only 10 percent used diet alone, and 1 percent used exercise only says the American Council on Exercise. Follow American College of Sports Medicine Guidelines and try to incorporate about an hour of moderate intensity cardiovascular activity five times per week to boost your weight loss results.