This is probably the most common question asked of anyone who is trying to lose weight, and the most common answer would be 3500 calories.

However, that is a very general answer and only relates to the amount of calories you have to burn off to lose 1 pound of body weight, but where do you have to burn them from?

For example, 1 pound of protein is 1814.37 calories and 1 pound of fat is 4082.33133 calories, so if you are able to burn only protein calories, you can lose a pound faster than if you have to burn only fat calories. But there is no way to pick and choose which kinds of calories to burn, so the rough average of 3500 calories is what is used.

In the lab, 3500 calories equals one pound of body weight (both proten and fat combined). This means that you have remove 3500 calories from your current, regular diet in order to lose one pound. This can be done by simply cutting out 500 extra calories a day for a 7 days (500 x 7 = 3500). However, this is only a theoretical number, because not only is the 3500 calorie guideline arbitrary, but everyone has a different metabolism that burns calories at different rates. Some people may have to remove 750 calories per day to see any results at all, while others may only need to remove 300 calories per day to see the same results.

One general way to check how many calories should be eaten for the day (calorie intake) versus how many you should be burning to lose a pound (calories burned) is to use a body fat calculator to first find your required calorie intake, or maintenance intake, based on your current activity level and your body measurements or current weight. Then reduce that maintainance intake by about 500 calories per day. However, as you lose weight and inches, you will need to keep returning to the body fat calculatpr to re-figure your calorie input vs calories burned in order to keep losing the desired weight week by week. If you stay too long at a single input/output level, without re-figuring it as needed, you may hit the dreaded “plateau” where your weight loss abruptly stops, or worse, you may start gaining your weight back again.

You may be tempted to play with the simple math here, and also tempted to think that you can cut thousands of calories in a day and burn thousands more to drop a lot of pounds at the snap of your fingers, but that is not the case in the real world. Weight loss happens gradually, whether we like it or not.

However, if 1 pound per week isn’t fast enough for you and you want to reduce your calorie intake down even more, that is OK, but never decrease your intake to lower than 1500 calories per day. This lack of energy will cause your body to react by slowing down your metabolism down and storing as much of the food as it can in order to protect you against starvation. Of course, once you start eating normal amounts of food again, your body will still be in a metabolic state of trying to store as much as it can. This could take months for your metabolism to speed back up to normal and this is often what causes you to gain back the weight you lost, plus more.

One of the most frustrating things that a dieter notices is that as we eat less calories, our bodies burn calories at a slower rate. In other words, our metabolism decreases with a decrease in caloric intake.

It is believed that this occurs to aid in our own survival, so the body starts to store everything we eat as fat, just in case we have hit a “famine” situation. Or it may be simply because the body has been “comfortable” at that weight for a long time, and changing the status quo is not something the brain wants to do. This is a very real phenomenon called “diet-induced adaptive thermogenesis”. Basically, when you fail to burn as many calories as you once did, it can get harder and harder to decrease enough calories in your meals to lose even a single pound. This is even more frustrating when you know you should never go below a 1500-calorie daily intake, or that can shut down your metabolism completely.

It is more realistic to expect weight to drop off gradually, and it is more lasting if it is a gradual loss, because you are learning good eating habits along the way than if you are dropping the weigh using fad methods that cannot be maintained long-term. For example, if you skip meals trying to lower your caloric intake, especially below that 1500-calorie mark, that can actually have a negative effect by slowing down your metabolism, which can take months to bring back to its original high level.

However, even scientists aren’t sure at what level the metabolism slows down when you’re dieting. Does it kick in or out at a particular threshold? Does it always happen when you have a calorie deficit? It you are dieting at a reasonable calorie intake, then this should be a slight variable, but even so, a metabolism slow down could throw off that 3500 calorie ‘rule”. Different studies have shown that the metabolism slows down as much as 15% when you are eating under 800 calories per day, although another study has said that it slows only 7% to 12% if you are eating a 500-calorie diet. Still others show an even higher percentage of metabolic slow down that appears to be a nearly complete shut-down, which only goes to shows that study data is not consistent. Or is it?

The best way to keep your metabolism running at a high level, is to eat 4 to 6 small meals and snacks, each containing at least one serving of protein, evenly spaced out throughout the day. Not only will this help to keep your blood sugar stabilized and insulin levels on an even keel, but it will allow the body to expect to be fed regularly, and therefore will allow the fat cells to empty themselves so that you can lose weight.

This type of eating style will also provide consistent energy while maintaining your metabolism, and because of the protein, which takes more calories to turn into glucose fuel than carbohydrates do, it will help you resist snack attacks or extreme hunger between meals.

Your metabolism is also kept moving at a higher pace if you are engaging in regular exercise, and stays high for an hour or more after exercise, so the longer you can keep your metabolism in high gear, the faster you can burn off calories, even while sleeping.

In fact, unless you are walking around with a device that constantly measures how much oxygen you consume and convert to carbon dioxide; how much water is consumed or excreted; how much food is consumed and excreted; you can never really know how many calories are actually being burned by your own body, or even how many are being consumed and utilized, even if you weigh all your food. There will always be an uncertainty because everyone’s metabolic rate is different, and so are the calories in any one food. Yes, a tiny apple has only 50 calories, but it MAY have 45 or even 65 depending on the calorie chart you use, the variety of apple, or even the quality of the tree it came from. Your scales may not be precisely calibrated to give an accurate weight. So, even your calorie intake cannot be accurately determined. Add to that, food labels lie, restaurants lie, and our eyes lie.

To make matters worse, you can carefully weigh your food and diligently eat your “correct” calories, and work out according to your favorite burn chart, so that you have your 3500 calorie deficit for the week, and then find you have gained 3 pounds instead of lost them. This could be due to “water retention weight” from too much sodium in your diet, or, if you have also been working out, due to building more muscle. Muscle weighs more than fat, and muscle is instrumental in helping the metabolism in burning fat.

Which brings us to another disturbing point. How many calories that get burned from intentional exercising is also a theoretical number on the multitudes of charts available. Exercise machine read-outs are notoriously unreliable, and the web calculators aren’t much better because comparing the numbers from different site calculators will give you different answers. The activities in the charts may or may not be set up for your particular speed or intensity, and are often based on only a single body weigh. Plus, we don’t know how the intensity level for that particular exercise was measured, and we often do less intense exercise than we think we are doing. Add to this the paradox that people tend to be more active overall on days when they don’t work out because working out makes them tired and also contributes to overeating in order to replenish the body’s fuel.

However, if you are not exercising enough, part of your weight loss could include losing muscle, which is not a good thing to lose, because that also affects your metabolism. It has been said that if you exercise for a minimum of 30 minutes a day, you will not lose muscle weight, only fat and/or water weight. In fact, if you exercise enough, you may actually gain some muscle weight which, as stated above, will help you burn fat more quickly because your muscles are what the body uses to burn off the the fat to begin with. Fat is muscle fuel.