One of the first questions people ask when starting to count calories is how many calories should i eat a day. The answer to this depends on both the calories you are burning and your weight loss goals.
If you consume the same number of calories as you burn, your weight should remain relatively constant. Creating a calorie deficit of 3500 calories over a period of time should result in about 1 pound of weight loss. So some of the questions that are needed here are to understand the calories you are burning a day as well as if you are aiming to maintain your weight or potentially lose weight.
Many sources recommend that to engage in consistent long term weight loss you should aim to lose about 1 to 2 pounds of weight a week. It has been suggested that if you attempt to lose weight at a rate that is faster than this, you risk losing lean muscle rather than fat. As muscle burns calories at a faster rate when at rest than fat, losing lean muscle may lower the calories you burn a day, and is thus counter productive to long term fat loss.
If you are aiming to lose 1 to 2 pounds a week, this would imply creating a calorie deficit of about 3500 to 7000 calories a week, or 500 to 1000 calories a day. If on the other hand you are aiming to maintain your current weight, you should simply aim to consume around the same number of calories that you burn.
This then brings us to the question of how many calories do i burn a day. There are a couple of approaches to this problem. A good way to get an initial estimate of the calories you burn is through the use of a BMR calculator or a calorie calculator such as the one at this site.
Your BMR (basal metabolic rate) is the calories you burn a day with no real activity or digestion occurring. There are a number of established methods to calculate an estimate of your BMR such as the Harris-Benedict equations or the fomula of MD Miffin and ST St Jeor. These methods compute an estimate of your BMR from personal factors such as your age, gender, weight and height and are most easily applied through the use of a dedicated calculator for the purpose.
You can then get an estimate of the calories you burn a day by multiplying your computed BMR by a factor that is dependent on how active you are. This BMR calculator will perform this calculation of your overall calories burned at the same time it calculates you BMR. We provide more information on the actual equations and factors involved in these calculations with our BMR calculator.
So an initial approach to estimating how many calories should i eat a day is to calculate the calories you burn a day with this BMR calculator and then either consume that many calories to maintain your weight or consume 500 to 1000 calories less than this estimate a day to lose about 1 to 2 pounds a week.
This method applies general equations, and as such will not be accurate in all cases. As you get more into practicing calorie counting you can refine your estimates by maintaining a journal. Such a journal can keep track of what you are eating, what exercises and activities you are engaging in and what weight loss or gain you are observing.
If your activity is relatively constant, your actual weight loss should help refine your estimate of the calories you are actually burning. If for example with a given diet and exercise routine, your weight is remaining constant, then you can assume you are burning around the same amount of calories as you are eating, and can start to adjust your estimates based on this fact.
Your journal will let you monitor your weight loss or gain over the long term as well as keeping a record of your foods to be able to total the calories in your diet. By recording your exercises as well, you can use a calories burned calculator to get an understanding of the calories typically burned in a given exercise or activity.
A few other considerations to keep in mind here are that some sources recommend that you should not lower your calorie consumption below your BMR and that women should not lower their calories below 1200 calories a day and men should not lower their calories below 1800 calories a day. If you are having problems creating a calorie deficit within these constraints, you may want to increase the amount of exercise you do to help with this, as this will increase the calories you are burning without lowering the calories you consume.
It is also important to seek professional medical advice before commencing a weight loss program, as a doctor will be able to help you with any factors that may be specific to your situation.