be as problematic, albeit for different reasons, as chronically
elevated insulin. The occasional higher-carb meal can be
helpful for optimizing various hormones and enhancing
exercise performance. The window after exercise is
generally the safest time for carbs (like sweet potatoes or
rice) to be consumed. Why post-workout? After a vigorous
workout, your muscles actually pull sugar from your blood.
We’ll explore the idea of post-workout carbs further in
chapter 6.
Another problem is that the glycemic index refers to the
food ingested in isolation—and the impact of a slice of
bread, for example, would be very different when eaten
alone versus with fat and protein in a sandwich. As far back
as 1983, scientists have known that while adding fat to a
carbohydrate meal can reduce the glucose spike, it also
increases the amount of insulin released.^21 Put simply, fat
can cause the pancreas to overrespond, secreting more
insulin for the same amount of carbs! (In reality, fat only
delays the entry of glucose into the blood, but prolongs the
elevation of blood sugar.)^22 This makes the advice often
given to those looking to lower the blood sugar impact of
foods—to add more fat to a carbohydrate meal to lessen the
glycemic spike—misguided.
Other metrics, then, are needed to discuss the hormonal
and metabolic impacts of carbohydrate ingestion. Two that
are currently under study are the glycemic load and insulin
AUC (or area under the curve) for a given meal. Glycemic