Adding Fat or Protein. The previously mentioned study by Foster et al. (1979) co

Question

Adding Fat or Protein.

The previously mentioned study by Foster et al. (1979) compared milk, which contains a mix of macronutrients, to glucose or water fed prior to exercise. The glycemic response to milk ingestion was less than that of glucose prior to exercise. Although the blood glucose concentration dropped at the start of exercise after milk ingestion, it later rose above that observed during the glucose trial. Serum fatty acid concentration during exercise was higher for milk (the lower glycemic index food) than for glucose. Performance after milk ingestion was improved relative to the glucose trial but was not superior to the control trial.

19.Explain the findings above using your knowledge of Biochemistry.

Explanation / Answer

The facts can be explained as below:

Case 1: Milk ingestion: As the person ingested milk and exercised, his body required large amount of energy. Due to low glycemic index of milk as compared to glucose, the milk sugars were quickly exhausted and his body shifted to utilization of other preferred sources of energy. Fats remain stored in the body and represent to be a preferred source of energy when required. Thus, fatty acid oxidation suddenly increased. However, as the insulin levels were suddenly increased during exercise, the negative feedback loop inhibition prevented further plasma clearance of sugars and hence insulin release was halted in the body. This enhanced the blood glucose levels suddenly.

Case 2: Glucose ingestion: As the body required energy quickly and large amount of glucose was already present in the body, the person combusted this sugar to gain energy and thus, does not require other sources of energy such as fatty acid oxidation. Since the blood glucose levels, hence the insulin levels were maintained throughout, the plasma glucose levels did not elevated too much after end of exercise.

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