Metabolism - Over-eating and Under-eating

Question 1

Over-Eating

Answer 1

When excess calories are consumed:
* Carbohydrates (CHOs) are preferentially used for immediate energy under normal conditions.
o Excessive CHOs, especially when refined (combined with a sedentary lifestyle), will force the metabolism into DNL - a key driver of ‘Metabolic Syndrome’.
* Fructose is the carbohydrate exception regarding DNL:
o The liver easily converts fructose into fatty acids. High amounts of fructose result in high levels of de novo lipogenesis.
* Fats that are consumed in excess of energy requirements are stored in adipose tissue under normal metabolic conditions.
De novo lipogenesis (DNL) = the metabolic pathway that synthesises fatty acids from excess carbohydrates

Note: converting CHOs into body fat (DNL) is a costly process requiring up to 30% of the CHO energy to do so

Question 2

Under-Eating

Answer 2

Consuming fewer calories than needed to meet energy requirements (i.e. a negative energy balance) forces the body to use stored fat for energy (i.e. weight loss).
* However, chronic calorie restriction may lead to a slowing down of one’s metabolism (as well as micronutrient deficiencies).
* This can make it more difficult to continue losing weight.
* A person may need to eat more food (but the right types – i.e. nutrient dense) to help re-establish a healthy metabolism for weight loss to continue.

Question 3

De novo lipogenesis (DNL)

Answer 3

De novo lipogenesis (DNL) = the metabolic pathway that synthesises fatty acids from excess carbohydrates