How Can a Diet High in Carbohydrates Cause Obesity?

Our bodies make fats and store them for energy in a process called de Novo Lipogenesis. In this process the body utilizes carbohydrates and amino acids to create triglycerides or phospholipids. De Novo Lipogenesis will occur in our bodies under high glucose and high energy levels because it needs a lot of the intermediates these produce (mainly Acetyl-CoA, NADPH and ATP). So one may think that if they’re eating a lot of carbohydrates they would be utilized in this process, but they would be wrong for thinking so. According to the “Dual Macronutrient Hypothesis” our bodies will preferentially utilized carbohydrates as fuel if they are present. When we break down fat to use as energy, it is a much more costly and slow process so the body will choose to use more readily available energy sources like carbohydrates. When we ingest excessive amounts of carbohydrates dietary fats are spared, so they get stored and de novo fats are spared by essentially turning off lipogenesis. The sparing process occurs by a couple of mechanism these include: preventing beta oxidation or the breakdown of fatty acids and preventing lipolysis or the breakdown of lipids. So then, if we eat an excessive amount of carbohydrates then not only have we turned off breaking down our stored fat as energy, we’re eating too many carbohydrates to break them down as well so the rest will get converted to fat and then stored as well. Eating excessive carbohydrates will cause weight gain because we preferentially use carbs as energy.