Food digestion is too complex and messy to provide a number for each serving of food you eat. In addition, each person’s digestive ability changes how many calories are absorbed. Food is energy for the body which requires digestive enzymes in the mouth, stomach and small intestine to break it into molecules that cells can use.
The calorie notation listed on a label or quoted in a food composition book is calculated by the amount of energy required to heat one kilogram of water one degree Celsius. Fats provide about 9 calories per gram, carbohydrates and protein deliver four calories per gram. These calculations were approximations from a 1950’s laboratory analysis and have never been replicated.
New research is indicating this is far too simplistic. To accurately calculate the calories a person gets out of a given food, you need to factor in whether it is boiled, baked, fried or micro-waved; how much energy the body expends to break down the food, and to what extent the food survived digestion and bacteria enrichment before transport into the bloodstream.
Every food is digested in its own way. Plant foods involve stems, leaves and roots. Older leaves are tougher than young ones so digestion differs based on age. Cooking breaks down cell walls in the plant but boiling, steaming and microwaving result in different textures and digestive processes. Nuts and seeds are hard to digest with peanuts, pistachios and almonds less digested than other foods with similar protein and fat. A USDA study in the American Journal of Clinical Nutrition, August 2012 showed significant amounts of undigested almonds in feces of the people in the study. Many of the calories and nutrients in the almonds were not available for energy and cell metabolism.
Cooking food allowed humans to consume more calories and increased the nutrition extracted from it. Heat allows meat to be more digestible and kills bacteria. Food processors use flour, sugar, and fats to produce thousands of food-like products for increased energy consumption. These processed foods are so easily digested in the stomach and small intestine that obesity is now a major public health problem.
Counting calories is NOT accurate and the calories on a food label are a LIE. Instead, eat whole grains, raw fruits and vegetables (or lightly steamed), and lean proteins (fish, grass-fed beef, pork) and healthy fats (avocado, olive oil, raw butter) to get daily nutrients.