As one's sole race nutrition, the fat content would be way too high to be optimal. M&Ms are ~ 37% fat calories and that much fat would slow stomach emptying, digestion and absorption. Your body already has plenty of fat for just about any race imaginable. It's carbs that we will run short on. That said, as a small treat during a race they might be quite wonderful and as fuel during a low intensity long ride they should be usable as well.

YMMV,

Hugh

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Genetics load the gun, lifestyle pulls the trigger.