Determining the minimum calories needed to survive is not an exact science. However, it is possible to get pretty close to an ideal range you can aim for most days of the week. Eating in this range can help power you while performing daily tasks, when you're on the go, at work or during a workout.
The number of calories you need to survive depends on your age, weight, activity level and gender. For long-term health, most people will need a minimum of 1,200 calories per day.
Minimum Calories Needed to Survive
While surviving on very few calories for a brief time might be possible, it's not sustainable. The minimum calories needed to survive depends on a variety of factors including your weight, age, activity level and being male or female.
The UCLA Center for Human Nutrition says that eating fewer than 1,000 calories per day has the same effect physiologically as total starvation. With that in mind, it makes sense that the USDA Dietary Guidelines recommend a much higher calorie level for health.
According to their calculations, sedentary females aged 26 to 50 need 1,800 calories per day and sedentary men aged 26 to 40 need 2,400 calories per day. When men get 40 and above, their calorie needs decrease by 200 calories. Add in some moderate activity, and that same female is now needing 2,000 calories and an active man needs 2,600 calories.
Reducing calories below what is recommended for general health is sometimes referred to as a very-low-calorie-diet or VLCD. A VLCD is defined medically as a diet of 800 calories per day or less. These programs are medically supervised and are primarily used for morbidly obese individuals wanting to lose three to five pounds a week.
Negative Effects of Low Calories
If you're not fueling your body with enough food, and consequently not enough calories, you might not be getting the nutrients you need for optimal health. Vitamins, minerals, fiber and other nutrients are key to helping your body and brain perform at peak levels. In an attempt cut calories, many people limit or even reduce carbohydrates from their diet.
When you restrict carbohydrates in an effort to only eat the bare minimum calories to survive, you miss out on the health benefits of fiber, which is a type of carbohydrate the body can't digest. In addition to making you feel fuller for longer, fiber also regulates the body's use of sugars, lowers blood cholesterol, helps to promote regularity and prevent constipation, and it may even lower the risk of heart disease, according to Harvard T.H. Chan School of Public Health.
Another downside of only eating the minimum calories to survive is the impact it has on your metabolism. The Academy of Nutrition and Dietetics says if you're not taking in enough calories, your body goes into survival mode and your metabolism slows down in an effort to conserve energy. You also risk not getting enough calcium, which increases your risk for osteoporosis and hip fractures.
Tips for a Healthy Diet
Spending a few days eating the minimum calories needed to survive is not going to cause any long-term damage. That said, designing an eating plan that focuses on lifestyle modifications rather than a restrictive diet, is going to help you make permanent changes that can last a lifetime.
To get started on a healthy eating plan that meets your needs, the first step is to determine the number of calories you need to eat each day. You can do this by using the USDA Dietary Guidelines chart. Once you have the baseline number, of the number of calories you need to eat when sedentary, you can factor in your activity level. Remember, these amounts represent what you need to eat to maintain your current weight.
If you want to lose weight, the Mayo Clinic suggests reducing your calorie level by 500 a day. Doing this can help you lose one pound per week. To increase weight loss, even more, consider adding in daily exercise. Not only does exercise help you lose weight, but it also helps you keep it off, according to a March 2019 study from the University of Colorado Anschutz Health and Wellness Center, published in Obesity.
- U.S. Department of Agriculture, Office of Disease Prevention and Health Promotion: "Estimated Calories Needed per Day, by Age, Sex, and Physical Activity Level"
- Harvard T.H. Chan School of Public Health: "Fiber"
- Academy of Nutrition and Dietetics: "4 Ways Low-Calorie Diets Can Sabotage Your Health"
- UCLA Health: "Very Low Calorie Diet (VLCD)"
- University of Colorado Anschutz Medical Campus: "Study: Exercise is More Critical Than Diet to Maintain Weight Loss"
- The Mayo Clinic: "Fast Weight Loss: What's Wrong With It?"