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Extra protein doesn't turn to fat
At a roundtable of prominent physicians, the claim came up that the only reason to go above the RDA of 0.8 grams per kilogram is resistance training, and that anything above it turns to fat for people who are not lifting. The first pathway for protein is oxidation. The body uses it, burns it, and also uses it for gluconeogenesis, the generation of glucose at a much slower rate.
The body has no need for carbohydrate but does have a need for protein, which is used for rebuilding. Calories from carbohydrates, fats, and proteins leave different biochemical footprints, and it is difficult to overfeed dietary protein. Protein also sends satiety signals to the brain, alongside leptin, ghrelin, and PYY, and it does a lot more than build muscle.
How does the body burn extra protein?
Liver cells strip the nitrogen off amino acids in a step called deamination. The nitrogen is converted to urea through the urea cycle, which Hans Krebs and Kurt Henseleit described in 1932, and the kidneys excrete it. The leftover carbon skeletons enter the same energy pathways as sugars and fats, or are used to make glucose.
Why is protein so hard to overeat?
In a 2005 study led by David Weigle at the University of Washington, volunteers raised protein from 15 to 30 percent of calories while carbohydrate stayed fixed. Without being told to eat less, they cut their daily intake by about 440 calories and lost weight. Protein raises satiety signals and has the highest thermic effect of the three macronutrients.
Why can the body make glucose without carbs?
The liver and kidneys build new glucose from amino acids, lactate, and glycerol, a process called gluconeogenesis. During prolonged fasting, ketones made from fat supply a large share of the brain's energy, which reduces how much glucose must be made. Red blood cells, which lack mitochondria, depend on glucose at all times.
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