I’ve posted a few times on this subject, but this is a new paper that’s hot off the presses. Once thought to help with weight loss, caffeine has recently been cast in a new light as actually contributing to weight gain. Even caffeinated diet pop can lead to weight gain, due to increased insulin secretion in the body.
A double-blind, randomized, placebo-controlled crossover study with periods of 7 days and washouts of 5 days comparing caffeine with placebo capsules was conducted. Participants were 16 healthy adults aged 18 to 22 years with a history of caffeine consumption. Blood samples from each subject were assayed for glucose, insulin, serum cortisol, DHEA, and androstenedione on the eighth day of each period after an overnight fast. Nighttime salivary melatonin was also measured. Insulin levels were significantly higher (by 1.80 muU/mL; 95% confidence interval, 0.33-3.28) after caffeine intake than after placebo. The homeostasis model assessment index of insulin sensitivity was reduced by 35% (95% confidence interval, 7%-62%) by caffeine. There were no differences in glucose, DHEA, androstenedione, and melatonin between treatment periods. This study provides evidence that daily caffeine intake reduces insulin sensitivity; the effect persists for at least a week and is evident up to 12 hours after administration.
Having excess insulin in your blood makes it hard for your body to break down fat, so in essence caffeine can slow weight loss efforts. You can read the whole paper here Beth.