How many calories do we need? Our bodies use a lot of calories just to exist. The amount of calories you need depends on your age, sex, height, activity level, current state of health, if you want to lose, gain or maintain your current weight status, and even your current body composition. For example, a 33 year old woman, who is 5’5”, 146 lbs, and is moderately active needs roughly 1450 calories a day just to continue living, and 2200 calories to maintain her activity level and current weight. In order words, her body burns over half of her needed intake of calories just to think, digest, generate new cells, fight disease, create hormones, and so on. She then needs to have enough activity in her day to burn the other 850 calories. If she plans on losing weight, she would need to reduce her caloric intake by about 300 calories, and increase her activity to burn another 200 calories. All of this was calculated by several scientific calculations, but even these various calculations can differ by up to 100 calories, so it can be hard to tell where to even begin. There are great online calculators to help give you an idea.
It is important to remember that your brain cannot reason with your body. You cannot tell your body that it’s being starved in order to give up its fat stores. Your body does not care.
That’s an extreme example, but one that’s used all too often for weight loss. Your best bet is to reduce calories less drastically, gradually adding in exercise. Reducing what you eat, especially food that are “empty calories” (explained next), and slowly increasing the amount you exercise will adapt your body better to a long-term change. The results may not happen as quickly, but health is for life. This is a lifestyle change for your better health.
There are still some “experts” out there who say that calories in/calories out is all that matters; you can eat junk food as long as you work it all off. This is bad advice. Yes, you could follow this method, and maybe lose weight in the short term, but eating foods that are low in health benefits will cost you over the long run. A study was done that compared the short-term effects of an apple vs. an oatmeal cookie supplemented in a weight-loss diet. Both the apple and the oatmeal cookie had the same amount of calories, and technically, oatmeal is a healthy option as a food. The caloric composition of the subjects diets were based on their metabolic rates and monitored and adjusted by a dietitian to promote weight loss. In the end, the apple supplement group had nearly twice the weight loss of the oatmeal cookie group, and their blood glucose levels were much better as well. The results show that whole foods like fruits and vegetables are a much better option for a balanced diet.
Processing food makes the calories, as well as other nutrients more available. Processing here means changing food from its raw state to one that is cooked. Cooking foods make it so your body doesn’t have to work as hard to get at the necessary energy and nutrients. Cooking is how we were able to become who we are today (take that, Paleo diet). Over-processing makes even more calories available by removing important components, such as fiber or certain fats, and/or adding undesirables, such as sugar. Over-processing can also change the chemical structure, making it hard for the body to process appropriately (see HFCS). Basically, over-processed foods take even less energy for your body to digest and absorb. Over-processing can make it hard to accurately measure the amount of calories in these foods, and some experts say that there could be a lot more calories in that food items than is on the label. This could be why we have seen such an increase in obesity in the last 50 years.
The best way to rev up your metabolism is through exercise, specifically exercise that builds muscle. This is why it is important to perform a combination of cardio and weight-bearing exercises. Cardio helps burn fat, as well as improve heart, lungs, and endurance. Weight bearing exercises improves lean tissue, bone mass. The more lean tissue you have, the higher your metabolism, which means your body will burn more calories, even when it’s at rest.
In the end, monitoring calories in and calories out is the closest thing we have to keeping some sort of balance. Especially when you first really start looking at how many calories are in some of your favorite foods and beverages. The problem with counting calories is it’s not an easy thing to keep up, and in the end, studies have shown that it doesn't lead to long-term weight maintenance. Think about it- do you really want to spend the rest of your life trying to stay under 1600 calories a day? Counting calories can make you very obsessive about food, and make social settings and travel very stressful. Food is supposed to be nourishing and enjoyable, not a source of panic.
My recommendation- eat whole foods, try to avoid processed foods, work with a dietitian to learn what choices to make that are right for you, and exercise!