Calories. A word you have probably heard used countless times by dietitians, and health and fitness gurus. But what does it actually mean? And what do calories have to do with weight loss and weight gain?

In this article, we shall explore the science behind calories, energy balance, and the dynamics of weight loss and weight gain.

What are calories?

A calorie is a unit of energy. In nutrition, the term refers to the energy individuals get from the carbohydrates, fats, proteins, and alcohol in the food and drink they consume, as well as the energy they use in physical activity.

Many people attach a negative connotation to calories, automatically correlating them with excess weight gain, but they are in fact extremely important for the normal functioning of the human body.

The key consideration when thinking about calories is whether or not you are getting the right amount for your body. If you consistently take in more energy than your body needs, you will see weight gain. On the other hand, if you consistently take in less energy than your body needs, you will see weight loss.

How many calories do you need every day?

The ideal daily calorie requirement for an individual will vary depending on factors like age, gender, metabolism, and levels of physical activity. The WHO advises a daily calorie intake of 2,000 calories a day for a person of healthy body weight.

According to the NHS, the recommended daily calorie intake is 2,000 calories for women, and 2,500 for men.

Some of the factors that may cause variation in how many calories you need include;

• Age: Growing children and teenagers may need more energy while sedentary elderly people may need less energy
• Size: Taller and heavier people will typically use up energy more rapidly and thus require more calories.
• Lifestyle: If you live a very active lifestyle for example regularly exercising or being a professional athlete, you will likely need more calories for energy
• Medical conditions: Generally, people who are acutely ill will expend more energy and thus need more calories. Certain medical conditions like hyperthyroidism also increase the body’s energy requirements.
• Medications: Certain medications like glucocorticoids may also raise your body’s energy needs.

How does calorie intake affect weight gain and weight loss?

Many people believe that a high calorie intake alone can cause weight gain. However, this is only partially true. In nutrition, the term “energy balance” is used to describe the balance of calories consumed through eating and drinking (energy in) compared to calories burned through physical activity and basic bodily functions (energy out).

In a state of perfect equilibrium, the value for “energy in” would be exactly equal to the value for “energy out”. However, variations of our daily diets and levels of activity make this impossible. But these small fluctuations in calorie intake and expenditure are insignificant in the long term as most people will find a healthy balance that allows them to stay at the same healthy weight.

For people who have a very high calorie intake and low physical activity, the energy balance equation is skewed. More energy is coming in than going out. The body uses what it needs, and any excess calories are converted to fat, which translates into weight gain over time.

For those with low calorie intakes compared to level of physical activity, the body remains in a state of calorie deficit, and there will be weight loss as the body breaks down its fat stores and, eventually, its protein reserves, to make up for the calorie deficit.

Good energy balance is important because both excessive weight gain and excessive weight loss are extremely harmful to the health. People who are overweight are more prone to illnesses like heart disease, diabetes mellitus, and hypertension. People who are underweight are at risk of conditions like anemia, osteoporosis, and reduced immunity.

How to maintain a healthy energy balance

The key to maintaining a healthy energy balance is ensuring you take in only as many calories as you need while maintaining a healthy level of physical activity. This means avoiding excess amounts of foods that are too high in empty calories for example junk food, sugars, deep-fried foods. However, do not starve yourself. Maintain a balanced healthy diet with carbohydrates, proteins, fruits, and vegetables. Exercise regularly to avoid surplus calories.

Remember, the key to a healthy body is not losing weight to fit esthetic standards. Speak to your healthcare provider about BMI assessment to give you an informed perspective on your weight and your health.

Innocent Immaculate Acan is a medical doctor and writer. She won the Writivism Short Story Prize in 2016 and has published an illustrated children’s book titled The Pearl Trotters in Black, Yellow, Red. She was part of the 2018 class of the Young and Emerging Leaders Project.