Energy in Food

South Wales Personal Trainer, gives us the low down on knowing just exactly how much energy is in the food we eat. I Personal Train Cardiff, members of the public at a Cardiff Health club and its amazing how many people do not realise how much energy they are consuming.

Food is an integral and very important part of our life. This is because food is our energy source. Energy needs vary massively between individuals and on a daily basis depending upon a number of factors including daily activity levels and body size. The energy in our diet comes from fat, carbohydrate, protein and alcohol.

Energy in food is represented in calories (Kcal). There are calories in the majority of foods. Fatty foods are high calorie, and foods such as salads and vegetables are very low calorie. In order to loose weight we need to build up a calorie deficit. We need to burn off more calories through physical activity and consume less through food. To gain weight we need to do the reverse (consume more than we burn off).

This does not mean that if we eat 1,500 calories a day you must burn off 1,600 through exercise. This is due to us being able to burn calories while sleeping, sitting down, due to the respiration and heating/cooling down of the body.

The amount of calories (Kcal) we burn throughout the day while doing no physical activity is referred to as our Basal Metabolic Rate or your metabolism. People's Basal Metabolic rate differs from person to person, due to height, weight, body fat and muscle mass.

Therefore to loose weight you must, burn off more calories than you consumes. If this is done over a sustained period weight loss will inevitably follow.

Daily calorie intake

U.K. Dietary reference values for energy. Note: This is an estimated average requirement

Age (years): Males (kcal) - Females (kcal)

19 - 49: 2550 - 1940
50 - 59: 2550 - 1900
60 - 64: 2380 - 1900
65 - 74: 2330 - 1900
75 + 2100 1810

These are often provided to show the average energy requirement of 2000 kcal for women and 2500 kcal for men. Some manufacturers now include this information on food labels.

Now that we can estimate how many calories we should be consuming a day, how do we know exactly how many calories there are in certain foods.

The amount of energy (kcal) in foods varies significantly. As can be seen from the table below; fat and alcohol contain significantly more energy per gram than protein and carbohydrate.

Nutrient kcals/g

Carbohydrate 4
Fat 9
Protein 4
Alcohol 7

Energy in food is measured in calories. A calorie is the amount of energy needed to heat a litre of water by one degree Celsius. Calories are important in terms of weight management. Weight gain is due to a calorie intake higher than expenditure.

All the food that we buy in tins and packets by law must tell us how many calories are in certain foods. The majority of foods now use the traffic light system. This gives us a colour (red, amber, green) to signify the amount of calories, fat, salt and sugar content. The exact number of calories, fat, salt and sugar should also be easily distinguished.