A calorie is a unit of energy. What many people do not realise is that there are two different kinds of calorie. A small calorie, or a gram calorie, is written with a lower case ?c? in scientific literature and has the symbol ?cal?. This calorie refers to the amount of energy that is required to raise the temperature of one gram of water by one degree Celsius. The large calorie, also known as the kilocalorie, is the calorie that most people think of when they hear the term, and it refers to the amount of energy required to raise one kilogram of water by one degree Celsius. Technically, this unit should be written as ?Cal? or ?kcal?, but most people, even nutritionists, do not do this. When the term calorie is used in the context of diet and nutrition, it is the kilocalorie that is being discussed.

Should you keep an eye on the calories you consume?

If you care about managing your weight, then calorie intake does matter. The food that we eat contains energy, and that energy is burned to provide energy for our bodies. Even when we are at rest, our bodies are burning energy. The number of kcal that we burn while we are at rest is called our base metabolic rate, or BMR. Day-to-day activity, whether sitting in front of a computer studying or engaging in intense exercise, burns calories too. If we consume fewer calories than we burn during a day, we will lose weight. If we eat more calories than we burn, we will gain weight.

As a general rule of thumb, a deficit of 3,500 kcal is required to lose 1lb of weight, and a similar surplus will cause weight gain. Note that the weight loss and gain will not always be fat loss or gain. If you have a lot of body fat to lose, then most of the loss will come from fat, but as you get closer to your ideal weight your body may start to take more of the weight from muscle stores, especially if you are not engaged in resistance training to encourage the body to hold on to muscle.

If you are eating a large calorie surplus, then your body will store that surplus as fat. If you are eating a smaller surplus and engaging in resistance training, then your body may use some of that surplus to add lean body mass.

Are All Calories Equal?

There is a lot of talk in weight loss circles about the concept of ?eating clean?. In many ways, the Paleo diet is a clean-eating diet because you do not eat junk food or a lot of simple carbohydrates. However, the Paleo diet does allow for the consumption of a large amount of fat. Advocates of clean eating believe that the type of calories that you consume is just as important, if not more important, than the number of kcal that you consume.

Whether or not you agree with this viewpoint will depend on your personal approach to dieting and your own goals. In terms of simple weight loss, a calorie is a calorie. If your total daily energy expenditure is 2500 kcal, you could lose weight if you lived on 2,000 kcal of ice cream per day, every day. Your overall health would suffer, and your body composition may suffer because the balance of macronutrients in your diet would not be very good. The three macronutrients are protein, carbohydrates and fat. You need some fat in your diet because fats are essential for hormone production. Proteins are used for muscle growth, and carbohydrates are a good source of energy.

However, most people are not interested in going to the extreme of living on just one food type. Eating clean does have some benefits when it comes to long-term weight loss. Firstly, if you cut junk food out of your diet, you are more likely to feel healthy and have more energy. Secondly, a lot of junk foods are designed with a balance of fat, salt and sugar that induces cravings and can trigger binge-eating. If eating clean helps to stop those cravings and improve your diet adherence, then by all means eat clean.

The opposite of the clean eating approach is the ?If It Fits Your Macros? approach. This approach is highly suitable for people who follow the Paleo diet. It means that you try to stay within your daily calorie allowance and hit your daily macronutrient target. If your goal is to consume no more than 30% of your daily calorie allowance from carbohydrates, and you have a lot of your allowance left over at the end of the day, then under the ‘If It Fits Your Macros’ approach you would be allowed to indulge in a carbohydrate-dense meal.

Do What Works for You

When it comes to diet and exercise, the best approach is the one that works for you. The impact of nutrient timing and macronutrient balance (within sensible limits) is debateable, but the impact of the number of kcal that you consume versus your TDEE is clear. Instead of worrying about whether you should eat one, six or three meals per day, or whether a few extra carbohydrates and fats will ruin your diet, focus on keeping the amount that you eat in check to match your goals.

The Paleo diet offers plenty of options for strength athletes, people who are trying to lose weight and people who engage in endurance exercise. Depending on your goals, you can skew the diet towards proteins, fats or complex carbohydrates. If you find that snacking throughout the day stops you from feeling hungry, then do that. If you prefer larger meals at specific times of the day to keep your energy levels up, then that works too. There is no right or wrong way to structure your diet. Unless you are a bodybuilder preparing for a contest, you should find that you will make good progress through a simple diet and exercise regimen.