Eating too little means consuming significantly fewer calories than your body needs for basic functions, often below 1200 calories for women or 1500 for men, leading to fatigue, slow metabolism, hair loss, and deficiencies, with general guidelines suggesting women need 1800-2400 and men 2000-3200 calories daily, depending on activity, age, and body size.
This can vary widely based on factors such as age, sex, weight, height, and activity level. As a general guideline: Women: Consuming fewer than 1200 calories per day may be considered undereating. Men: Consuming fewer than 1500 calories per day may be considered undereating. However, these numbers can vary.
A normal amount of food to eat in a day will vary from person to person. This will depend on factors such as height, age, sex, activity levels, and genetics. In general, however, it includes three balanced meals. A typical adult needs around 2,000 to 2,500 calories daily.
“Everyone's body is different, but for most people, eating less than 1,200 calories a day could slow your metabolism enough to make it harder to lose weight,” says Uy. Some signs you have low metabolism include: Weight loss progress that has slowed down. You feel tired or low energy throughout the day.
Understanding the 3-3-3 Rule
Specifically, the rule suggests: Three balanced meals per day. Three hours between each meal. Three hours of movement per week.
OMAD is not suitable for everyone. Studies show that eating only once a day may increase blood pressure and cholesterol levels, especially if the single meal consists of heavily processed or high-carb foods. Other potential risks of fasting include: Shakiness or physical weakness.
For example, the loss of water might make you feel a little lighter, but you're not getting rid of belly fat. It's just a loss of water. Try to choose an eating pattern that you can maintain over time. Even if you lose a few pounds on a 3-day cleanse or fast, these types of diets aren't sustainable over a long period.
Consuming at least 1,200 calories per day has often been touted as the minimum for basic bodily functions and to stay out of starvation mode, but the amount is actually too low. A healthy amount of calories for adult women ranges from 1,800 to 2,400 calories per day and for men it's 2,000 to 3,200 calories per day.
Fortunately, lifestyle changes and addressing underlying causes can help to speed up the metabolism.
One cheat day will not lead to weight gain. If you notice an increase in your weight on the scales after a cheat day, it is likely water retention.
Popular Japanese weight loss "tricks" focus on mindful eating, smaller portions, and increased daily movement, like the Hara Hachi Bu principle (eating until 80% full), using small dishes for portion control, incorporating green tea and fermented foods for gut health, and practicing mindful walking or interval walking, rather than a single magic solution. While some online trends like the pink salt water drink exist, they often combine these healthier Japanese lifestyle habits with marketing, emphasizing portion awareness, gentle activity, and a balanced diet.
How Much Food You Need. The basic rule of thumb is that you need one calorie per minute to sustain your basal metabolism. That works out to just over 1,400 calories per day, which is what the average human burns at rest. Normal activity levels burn another 1,000 calories, bringing the daily total to 2,400.
There's no single "number 1" unhealthy food, but ultra-processed items like sugary drinks, processed meats (bacon, hot dogs), deep-fried foods (fries), and refined snacks (donuts, chips, sugary cereals) consistently top lists due to high sugar, salt, unhealthy fats, and additives linked to obesity, heart disease, and diabetes. These items offer little nutritional value while increasing risks for chronic diseases.
Signs and symptoms that a person may not be eating enough include:
The 3-3-3 rule for weight loss is a simple, habit-based method focusing on three key areas: 3 balanced meals a day, 3 bottles (or ~1.5L) of water by 3 PM, and 3 hours of physical activity per week, aiming for consistency over complex diets. It simplifies fat loss by establishing rhythm through consistent eating, adequate hydration to support metabolism, and regular movement, promoting sustainable health without intense calorie counting or restrictive rules, says Five Diamond Fitness and Wellness, Joon Medical Wellness & Aesthetics, and EatingWell.
Symptoms of starvation mode
Your metabolic rate does change during your early life, but it plateaus between the ages of 20 and 60, and only decreases by around 1% per year after that. Your total daily energy expenditure also depends on your weight. So, if your body composition changes, your energy expenditure will also change.
Boosts Your Metabolism
Drinking water helps the body burn fat. Studies show that drinking 17 ounces of water can increase the metabolic rate by 30% in both men and women. Even mild dehydration can slow down metabolic rate by 3%.
Foods That Are Metabolism Killers
However, calorie intake should not fall below 1,200 a day in women or 1,500 a day in men, except under the supervision of a health professional. Eating too few calories can endanger your health by depriving you of needed nutrients.
Survival Scenarios: The Minimum Food Intake
Research indicates that a person can survive for several days—sometimes up to a week—on minimal food, particularly if well-hydrated. Caloric Needs: A rough estimate is that an adult can survive on around 800 to 1,200 calories per day if absolutely necessary.
It Can Lead to Nutrient Deficiencies
A 1200-calorie diet doesn't leave much room for a variety of nutrient-dense foods. With such a low caloric intake, it's extremely difficult to meet your body's needs for vitamins, minerals, and other essential nutrients.
Some studies suggest that sleep plays a role in weight loss, and specifically fat loss, during calorie restriction. In a study of people undergoing 14 days of calorie restriction, the participants lost less fat when they spent 5.5 h a day in bed than when they spent 8.5 h a day in bed [40].