Delaying morning coffee improves its metabolic impact, experts say

Research highlighted in French health outlets notes that drinking coffee immediately after waking coincides with the body's natural cortisol peak, which occurs about 30‑45 minutes after rising. Consuming caffeine during this window can blunt its effectiveness because cortisol and caffeine interact, reducing the boost in alertness and potentially disrupting the natural cortisol rhythm.

Waiting roughly 90 minutes before the first cup allows cortisol levels to fall, making caffeine more effective at blocking adenosine receptors. This timing can enhance the modest metabolic effects of coffee, which include a short‑term increase in resting energy expenditure of 3‑11 % for a few hours, slight thermogenesis, and increased lipolysis. Studies also suggest minor influences on blood glucose regulation, though the overall impact on weight loss or long‑term health remains limited and varies between individuals.