The Obesity Epidemic: What Caused It? How Can We Stop It?

by Zoe Harcombe

thermic effect of nutrients (thermogenesis) is approximately 6-8% for carbohydrate, 2-3% for fat and 25-30% for protein. [29] I.e. approximately 6-8% of the calories consumed in the form of carbohydrate are used up in digesting the carbohydrate and turning it into fuel available to be used by the body. In contrast, 25-30% of the calories consumed in the form of protein are used up in digesting the protein and turning it into fuel available to be used by the body. This also makes intuitive sense; carbohydrates are relatively easy for the body to turn into energy (indeed they start being digested, and turned into glucose, with salivary enzymes, as soon as we start chewing). Protein needs to be broken down into amino acids, which is a far more complex process.