Calorie Count (Food and Activity) and Effect on Body Weight

What is the calorie count of food or exercise?

A calorie count is the amount of energy potential in foods and the energy expended in activity.  Energy is measured in calories or joules. Since the body uses so many tens of thousands of calories and joules every day, the kilocalorie (kCal) and kilojoule (kJ) are often better units to work with as each unit represents one thousand calories or joules. A single calorie or kilojoule is too small a unit. For example 50 kCal actually means 50,000 calories just as 50 kJ would mean 50,000 kilojoules. For convenience and over time, kCal fell away in weight management and calorie (Cal) took its place although Cal is intended to mean kCal.

Activity, as well, is measured in kilocalories which has just been assigned to the calorie value. A person’s basal metabolic rate (BMR) determines how much of calories are consumed at rest. Any additional activity will utilize more calories above and beyond the BMR. Standing and walking will consume more calories than sleeping whereas running, cycling or swimming will consume even more calories than standing and walking. Therefore a calorie count can be assigned to different activities – usually it is designated as the amount of calories expended per hour.

Calories to Lose or Gain Body Weight

The balance of energy determines the body’s fat stores and ultimately the weight. Food has an energy potential meaning that when consumed in can yield a certain amount of calories of energy. Therefore in weight management terms, the focus is on this energy potential of food rather than the weight of food. A simpler way to look at it is that a handful of nuts may be able to yield 300 calories of energy. The weight of the nuts are irrelevant. You can eat certain foods that weigh little but may be able to deliver a large amount of calories. Conversely you could a meal that weighs a lot but delivers a small amount of calories.

Activity involves expending energy and is proportional to the level of exertion – if you undertake strenuous activity, you will utilize more energy (calories) whereas if you are sedentary you will utilize less energy (calories). In a balanced state, the intake of energy (food calories) will equate to the expenditure of energy (activity calories). This will maintain a stable body weight.


Calories into Fat

The body has innate mechanisms to store as much energy (calories) as possible for later use. It is essentially a survival mechanism – calories are not wasted but utilized efficiently or stored for times of deprivation (starvation). Hormones such as insulin and glucagon are responsible for the immediate utilization, storage of calories and accessing stored calories. This is further influenced by the thyroid hormones and growth hormone.

All foods – carbohydrates, fats and proteins – can be used for energy. The body prefers carbohydrates but will use fat and protein if necessary. Fat stores in the body are in the form of triglycerides. An excess of calories, whether from carbohydrates, fats or proteins, will be stored as triglycerides in fat cells (adipocytes) which makes up the adipose tissue. The advantage of this storage form, fat, is that ounce-for-ounce it can yield more energy when needed than other forms like carbohydrates and protein. Fat is an efficient storage form.

Therefore when the calorie input in food is greater than the calorie output in activity, there will be weight gain.


Fat into Energy

People who are overweight or obese have an excess of fat tissue. This means that the stored calories are higher than normal. All human beings have some quantity of fat tissue but in the healthy body of the ideal BMI (body mass index), it is a moderate amount of fat – usually less than 20% of the body weight. In order to maintain these fat stores, the daily calorie input from food is greater than the calorie output in activity. This refutes the claims by some overweight or obese people that their food intake is minimal. Calorie-wise the intake has to be in excess to cause a higher than normal body weight but hormonal disorders may also have to be considered.

When the body needs additional energy but the immediate food intake and energy availability is too low, it will consume fat. Therefore fat stores will be reduced.  The concept in calorie counting for weight loss is to tip the scales in favor of the energy being expended (output calories). A person who is overweight or obese has to do one of two things :

  • Consume less calories by eating less food – lower calorie content, not just weight of food or portion sizes.
  • Use more calories by exercising, preferably cardiovascular exercise.

If this can be maintained regularly, weight loss will ensue over time. Once the ideal body weight is reached, the calorie input should match the calorie output.

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