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1. Lift. Muscle suck up glucose, improve (long term) sensitivity. 2. Eat fat/protein with sugary foods. Helps blunt the effect. [1] 3. Don't eat too many carbs. Even the AHA recommends below 60% because of other negatives. [2] 4. Eat the right carb sources. Starchy tubers are best: potatoes, yam/sweet potatoes, cassava and rice. And fruits like bananas, plantains and grapefruit. 5. Eat high GI foods unless your blood…
The carb sources you mention have very different GI loads. Potatoes are very high, Grapefruit is low. The rest are in between.
That said, it is relevant. Eating low GI and low carb generally is good for the obese and overweight. It'll do wonders against prediabetes and metabolic syndrome because they're insulin insensitive.
[1] Against the GI: http://wholehealthsource.blogspot.com/search?q=glycemic