The number of calories a human needs per day to survive depends on many factors, including age, gender, activity level, and overall health. While calorie needs vary significantly from person to person, there are some general guidelines for the bare minimum required for survival.
Quick Answer
The absolute bare minimum number of calories needed for a sedentary adult to survive is around 600 calories per day. However, this extreme low calorie intake should not be sustained for more than a few days. A more reasonable minimum that can be maintained longer term is around 1,200 calories per day for women and 1,500 calories per day for men.
Calorie Needs by Age and Gender
Calorie needs vary based on age, gender, and activity level. Here are some general estimates for calorie needs by age and gender for lightly active individuals:
- Children ages 2-3: 1,000-1,400 calories per day
- Children ages 4-8: 1,200-1,600 calories per day
- Girls ages 9-13: 1,600-2,000 calories per day
- Boys ages 9-13: 1,800-2,200 calories per day
- Girls ages 14-18: 1,800-2,400 calories per day
- Boys ages 14-18: 2,000-3,200 calories per day
- Women ages 19-30: 2,000-2,400 calories per day
- Men ages 19-30: 2,400-3,000 calories per day
- Women ages 31-50: 1,800-2,400 calories per day
- Men ages 31-50: 2,200-3,200 calories per day
- Women over 50: 1,600-2,400 calories per day
- Men over 50: 2,000-3,000 calories per day
As you can see, adult women generally need around 2,000 calories per day, while adult men need 2,500 calories or more per day. However, this can vary significantly based on activity level.
Calorie Needs Based on Activity Level
Activity level dramatically impacts calorie needs. Here is an overview of how calorie needs change based on activity level:
Sedentary
Sedentary individuals are those who get very little physical activity beyond basic daily movements. Examples include:
- Desk job with little walking
- Stay-at-home parent of older children
- Retired and mostly inactive
Calorie needs for a sedentary lifestyle are about:
- Women: 1,600 – 1,800 calories per day
- Men: 2,000 – 2,200 calories per day
Lightly Active
Lightly active individuals get 1-3 hours of exercise per week. Examples include:
- Office job with some walking
- Retired and active a few times a week
- Exercise 1-2 times per week
Calorie needs for a lightly active lifestyle are about:
- Women: 2,000 – 2,200 calories per day
- Men: 2,400 – 2,800 calories per day
Moderately Active
Moderately active individuals get 3-5 hours of moderate activity per week. Examples include:
- Office job with walking and standing
- Exercise 3-4 times per week
- On feet much of the day
Calorie needs for a moderately active lifestyle are about:
- Women: 2,000 – 2,400 calories per day
- Men: 2,600 – 3,000 calories per day
Very Active
Very active individuals get 6+ hours of moderate activity or 3+ hours of vigorous activity per week. Examples include:
- Construction worker
- Exercise 6 times per week
- Marathon training
Calorie needs for a very active lifestyle are about:
- Women: 2,400 – 2,800 calories per day
- Men: 3,000 – 3,600 calories per day
As you can see, calorie needs can vary by over 1,000 calories per day based on activity level alone. However, even among individuals of the same gender, age, and activity level, calorie needs can vary by hundreds of calories based on other factors like genetics and body composition.
The Minimum Number of Calories for Survival
So what is the absolute bare minimum number of calories a human can survive on? Here is an overview:
- 600 calories per day – the extreme minimum for survival in a sedentary adult. Restricting to this level should only be done for brief periods under medical supervision.
- 800-1,000 calories per day – the very minimum for a sedentary adult to maintain survival longer term. Should also be done under medical supervision.
- 1,200 calories per day – minimum for an adult woman to maintain survival long term.
- 1,500 calories per day – minimum for an adult man to maintain survival long term.
Consuming the bare minimum number of calories needed for basic survival should only be done for short periods of time. Very low calorie diets of 800-1,500 calories per day should only be followed under medical supervision to ensure nutritional needs are met.
Health Consequences of Consuming Too Few Calories
Consuming too few calories for an extended period can result in malnutrition, loss of muscle and bone mass, fatigue, hair loss, irregular periods in women, infertility, and other complications. Here is more on the health consequences of under-eating:
Impacts of Consuming Less Than 1,200 Calories Per Day
- Fatigue and weakness
- Headaches
- Dizziness and lightheadedness
- Reduced immune function
- Hair loss
- Irregular periods in women
- Brittle nails
- Infertility
- Nutrient deficiencies
Impacts of Consuming Less Than 800 Calories Per Day
- Extreme fatigue, dizziness, and disorientation
- Muscle loss and wasting
- Severe nutrient deficiencies
- Bone loss and osteoporosis
- Organ damage
- Heart arrhythmias
- Electrolyte imbalances
- Kidney stones
- Gallstones
- Death if maintained long term
Consuming too few calories can become life-threatening over time. Extreme calorie deficits should only be done for very brief periods and under medical supervision.
The Healthiest Minimum Calorie Intake
While it is possible to survive on fewer than 1,200 or 1,500 calories per day, this is not ideal for long-term health and wellbeing. Here are some healthier minimum calorie intakes to aim for:
- Sedentary women: 1,600-1,800 calories per day
- Sedentary men: 2,000-2,200 calories per day
- Moderately active women: 2,000-2,200 calories per day
- Moderately active men: 2,400-2,800 calories per day
Eating at these calorie levels can help provide enough energy for daily activities and reduce the likelihood of nutritional deficiencies. It also allows room in the diet for nutrient-dense foods like vegetables, fruits, whole grains, lean protein, and healthy fats. But calorie needs can vary significantly, so it is best to speak with a doctor or dietitian when determining your individual minimum calorie intake for optimal health.
Maintaining a Healthy Body Weight
Rather than targeting an extreme calorie restriction, a better goal is meeting your minimum calorie needs for health while staying within or working toward a healthy body weight. Here are some tips for maintaining a healthy body weight without overly restricting calories:
- Aim for a modest calorie deficit. Reducing daily calorie intake by 200-500 calories can promote gradual weight loss at a healthier pace.
- Weigh yourself weekly. This helps ensure you are not losing weight too rapidly.
- Eat plenty of filling foods like fruits, vegetables, whole grains, lean proteins, and healthy fats to help curb hunger.
- Exercise regularly to burn extra calories and build/maintain muscle mass.
- Get enough sleep and manage stress, as lack of sleep and high stress can increase appetite.
- Talk to your doctor if you have special nutritional needs or health conditions that impact your weight.
With proper nutrition and lifestyle habits, it is possible to reach and maintain a healthy body weight without extreme calorie restriction.
Example Calorie Intake Plans
Here are some examples of daily meal plans that meet minimum to moderate calorie intakes:
1,200 Calorie Day
| Meal | Foods | Calories |
|---|---|---|
| Breakfast | 1 cup Greek yogurt, 1/2 cup berries, 1/2 cup oats | 500 |
| Lunch | Veggie and hummus wrap with 1 oz turkey, salad with vinaigrette | 400 |
| Dinner | 3 oz salmon, 1 cup quinoa, 1 cup veggies | 500 |
| Snacks | 1 medium apple, 15 almonds | 200 |
| Total | 1,200 |
1,500 Calorie Day
| Meal | Foods | Calories |
|---|---|---|
| Breakfast | 2 eggs, 1/2 cup oats, 1/2 medium banana | 400 |
| Lunch | Tuna salad sandwich, 10 baby carrots | 450 |
| Dinner | 4 oz chicken, 1 cup brown rice, 1 cup veggies | 600 |
| Snacks | 1 oz nuts, 1 oz cheese | 300 |
| Total | 1,500 |
2,000 Calorie Day
| Meal | Foods | Calories |
|---|---|---|
| Breakfast | 2 eggs, 1.5 oz avocado, 1 slice toast | 500 |
| Lunch | 6 inch turkey sub, soup, salad with dressing | 700 |
| Dinner | 5 oz salmon, 1 cup brown rice, 1.5 cup veggies | 800 |
| Snacks | 20 almonds, 1 apple, 1 oz dark chocolate | 400 |
| Total | 2,000 |
These sample meal plans provide healthy, balanced nutrition while meeting minimum to moderate calorie needs. But optimal calorie intakes are highly individual and should be tailored to your specific needs and goals.
The Keys to Health on a Minimum Calorie Intake
While severely restricting calories can lead to health problems, it is possible to meet your basic caloric needs for survival and still enjoy good health. Here are some tips:
- Eat plenty of nutrient-dense foods like vegetables, fruits, whole grains, lean protein, dairy, beans, nuts, seeds, and healthy fats. Focus especially on getting protective vitamins, minerals, and antioxidants.
- Include protein at every meal. Getting at least 15-30 grams of protein per meal can help maintain muscle mass when calories are low.
- Strength train 2-3 times per week to build and preserve muscle.
- Take a multivitamin to help cover any potential nutritional gaps.
- Stay hydrated by drinking water, herbal tea, and other calorie-free beverages.
- Limit added sugars, refined grains, and saturated fats to reserve calories for more nutritious foods.
- Manage stress levels through exercise, meditation, social connection, and other relaxing activities.
Even at a minimum calorie intake, it is absolutely possible to get all the nutrients you need through real, whole foods. With strategic eating and lifestyle habits, you can stay healthy on limited calories.
When to Seek Medical Support
If you are considering an extreme calorie restricted diet for an extended period, it is important to work with your medical provider to ensure safety and meet nutritional needs. You may benefit from medical supervision if:
- You wish to consume less than 1,200 calories per day for longer than 1-2 weeks.
- You have a history of disordered eating.
- You take medications that may be affected by calorie restriction.
- You have a medical condition that impacts nutrition needs like diabetes, heart disease, etc.
- You are pregnant, breastfeeding, or trying to conceive.
- You are under 18 years old.
Consuming too few calories can have serious health impacts if done for too long without oversight. Work closely with your doctor to make sure your plan is safe and meets your individual health needs.
Conclusion
The minimum number of calories for basic human survival is around 600 calories per day for a short period, but 1,200 calories per day for women or 1,500 for men is safer for ongoing health. Consuming fewer calories should only be done under medical supervision. While calorie minimums vary based on age, gender, and activity level, it is healthiest to meet your basic caloric needs through nutritious foods and maintain a healthy body weight through modest deficits and lifestyle habits.
