Calories in food
The amount of energy in food is expressed as calories or kilocalories (Kcal) or kilojoules (KJ) where 1 kcal equals 4.184 KJ. Calories and kilocalories are used as synonyms however when we say calories it's really kilocalories we mean.
The energy in food comes from carbohydrates, fats and proteins and it is called food energy. After absorption from the gastro intestinal tract the "fuel" (the food elements now degraded into smaller parts) flows into the blood stream and the energy is released and utilized by the body's cells during respiration.
Fat has the largest amount of energy 9 kcal/g, while protein and carbohydrates contain 4,1 kcal/g.
The energy from the food is used for the body's basal metabolism, body temperature, to support the various physical activities and to build and maintain tissue.
The recommended daily energy from food for adult men is 2500 kcal and 2000 kcal for adult women. It's only a guideline and it depend on the weight and the activities so more active people will need more calories.
The energy in our daily food
The energy from our daily food includes, calories from fat, protein and carbohydrates, protein. Calories intake.
The energy (calories) from our daily food, should equal the basal body metabolism and the heat energy that is produced by our muscles - if we should maintain our current weight.
If there is a deficit in calories intake fat and protein (muscles) are used as fuel and burnt and if the the calories intake is more that needed the excess calories is stored as fat and obesity results.
Basal needs for an adult person in rest is about 2000-2500 kcal per day.
In addition 500-3000 kcal daily or more is required to cover the physical activities.
Protein. We need about 1 g of protein per kg body weight. The protein should contain sufficient amount of the 8 essential amino acids. Proteins from fish, meat and eggs are good sources of the amino acids that our body needs for building protein (fx. muscles). 1 g of protein contains 4.1 cal.
Proteins from plants usually is not as valuable as a source of the essential amino acids because usually a certain plant miss one or two of the essential amino acids and to make a good diet from plants only it is necessary to use different plant protein sources to provide the body sufficient amount of all 8 essential amino acids.
Fat is the most compact form of energy as food. 1 gr of fat contains 9 kcal. Thus Fat is used by our body as a storage of calories. Fat is stored either subcutaneous around the belly, thigh and buttocks and inside our belly as fat storage around the internal organs resulting in a big belly.
We need a certain amount of essential fatty acids, but as soon at these are meet we can live on a very low fat diet. Carbohydrate is the cheapest source of calories and usually carbohydrates are half or more of our daily intake of calories. 1 gr. of carbohydrate equals about 4.1 kcal.
Calories in food
1 gr. Pure Food fat = 9 KCal
1 g of body Fat = 7.72 Cal (KCal)
1 pound of body fat (0.4536 Kg) = 3.500 Cals (KCal)
Bodyfat is not pure fat like food fat. Bodyfat contains some water and blood therefore fewer cal than pure fat from food
Joule and Calories 1 KiloCal (KCal) = 4.18 KiloJoule (KJ)
Gain or lose weight compared to your daily calories you need to maintain weight
to gain 1 pound. Eat 3.500 Cals extra
to lose 1 pound. Save 3.500 Cals
Food Calories Table
Calories per 100 gr. / 3.5 oz
Meat ad 50-100 cal for fried meat
100 gr. 3.5 oz
100 gr.3.5 oz
pork, ham boiled
beef boiled, roast
beef, lamb, pork. lean
beef, lamb, pork. some fat
chicken. lean, no skin
egg. boiled per pc. 80 cal