Women generally require fewer calories for weight loss than men.
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Successful weight loss depends not only on eating fewer calories, but also on eating enough calories to make your diet sustainable and healthy. No single calorie intake is right for everyone, and how many calories you need depends on your gender, age, activity level and other individual factors, such as your metabolism and genetics. One thing is certain, however: Women should not eat fewer than 1,200 calories per day, and men shouldn't go lower than 1,500 calories daily.
Estimating Calorie Needs
To get an idea of how many calories you need to lose weight, you first need an idea of how many calories you should be eating to maintain your weight. According to the USDA, sedentary men need 2,200 to 2,400 calories daily; moderately active men need 2,400 to 2,800 calories; active men need 2,600 to 3,000 calories. Sedentary women need 1,600 to 2,000 calories; moderately active women need 1,800 to 2,200 calories, and active women need 2,000 to 2,400 calories each day.
Typically, older adults need fewer calories than younger adults. Of course, these are just estimates, and your actual calorie needs could be more or less. Your doctor or a nutritionist can help you figure out a more exact number.
Decreasing Calories for Weight Loss
Many people eat more calories each day than they need for weight maintenance, reports the Office of Disease Prevention and Health Promotion. Just making an adjustment to get yourself to your weight-maintenance calorie requirements can result in weight loss. If you are eating 500 more calories each day than you need, you could lose about a pound a week if you cut those 500 calories.
Start with a reduction of 500 calories per day. That's about the amount of calories in a small container of low-fat strawberry Greek yogurt, a can of soda and three small cookies. If you are a sedentary female, that reduction may bring you close to the minimum of 1,200 calories per day, which is a good place to stay until you reach your goals.
If you are a more active woman or a man, you can reduce your calorie intake by another 500 calories per day if you want to lose more weight or lose weight faster. Weight loss of 1 to 2 pounds per week is safe, but more than that could have negative effects. Keep in mind that you shouldn't go below that 1,200- or 1,500-calorie limit. If, for example, you are a moderately active adult female, reducing your calorie intake by 1,000 calories would put you below the minimum and would possibly be unsafe.
Problems With Eating Too Few Calories
Not eating enough while dieting can hinder your success. Drastically reducing your calorie intake can actually slow your metabolism, because your body is trying to conserve energy. For most people, the metabolism slowdown is minor and will correct itself once you start eating sufficient calories, but in extreme cases the effects can be long-lasting. For example, a 2016 study that examined the metabolic adaptations of participants on "The Biggest Loser" six years after their televised dramatic weight loss found that the adaptations persisted over time, resulting in long-term slowed metabolism.
Another issue is sustainability and risk of nutritional deficiencies. Unless you are following a medically supervised very low calorie diet that is carefully formulated for both satiety and nutritional completeness, it is highly likely you will have difficulty sticking with vastly reduced calorie consumption. You may also suffer nutritional deficiencies that can leave you feeling at best fatigued and foggy-headed and at worst seriously ill.