Depending on the person most people need between 1,600 calories to 2,600 calories per day to be healthy.
Recommended daily calorie intakes in the US are around 2,500 for men and 2,000 for women.
Eating a big breakfast could help with weight reduction and maintenance.
The brain uses around 20 percent of the energy used in the human body.
A 1,200-calorie diet is much too low for most people and can result in negative side effects like dizziness, extreme hunger, nausea, micronutrient deficiencies, fatigue, headaches, and gallstones ( 23 ).
Furthermore, a 1,200-calorie diet can set you up for failure if long-term weight loss is your goal.
When it comes to losing weight, a general rule of thumb is to consume 500 fewer calories than needed to maintain your present weight.
Doing this every day can help you lose about 1 pound per week.
It's difficult to get good nutrition and feel satisfied on a very low-calorie diet. In addition, consuming as few as 800 calories daily may not give you the energy you need for daily living and regular physical activity, especially if you eat the same foods every day.
If you want to lose 5 pounds in a week, you will need to reduce your food intake by 17,500 calories, which is a huge calorie deficit.
If you weigh 250-pound, you will need to reduce your daily calorie intake to about 1,250 calories per day, an amount which is too low amounting to starvation.