Cons
The GI index can be misleading, as foods with a high GI are not necessarily unhealthy and the reverse is also true. For example, watermelon and parsnips have a high GI value, but chocolate cake has a lower GI value – which would you choose?
Some foods which are high in fat, such as crisps, have a low GI value due to being cooked in fat, which slows the absorption of carbs in the body. If you’re not on the ball, it can be very easy to embark upon an unbalanced diet while following the principles of GI.
It means learning the GI values of foods which can be confusing, and it’s easy to make mistakes.