Want to lower your body fat? Coffee might an option. (Photo by annais)
Adiponectin is a protein hormone that modulates several metabolic processes related to weight gain. Adiponectin levels are inversely correlated with body fat percentage (link) – for example, diabetics have lower levels of adiponectin than non-diabetics, and losing weight increases adiponectin levels.
Since adiponectin affects glucose uptake and insulin sensitivity, and low adiponectin levels are a risk factor for developing diabetes and metabolic syndrome, it raises the question of whether increasing adiponectin levels might be a good thing.
A study from last year looked at the effects of coffee on adiponectin levels in 665 Japanese males (link). Adiponectin levels were measured from serum samples, and coffee consumption was assessed using a self-administered questionnaire. The questionnaire also included green tea consumption, so that the effects of green tea and coffee could be compared.
The participants who drank more coffee tended to be younger, more likely to smoke, and less likely to drink alcohol. The mean age of non-drinkers was 49.9, while the mean age of those who drank at least three cups per day was 48.2. Interestingly, non-drinkers had the highest mean blood pressure (systolic 129.5 and diastolic 80.7 mmHg) of all groups, while those who drank 1-2 cups per day had the lowest (123.1 and 76.7) – although this could just be due to the age difference. There were no significant differences in BMI or physical activity between coffee drinkers and non-drinkers. Unfortunately, body fat percentage was not measured.
However, adiponectin levels were significantly higher in those who drank coffee compared to non-drinkers. In those who drank none, 1–5 cups per week, 1–2 cups per day, and >2 cups per day, adiponectin levels were 5.95, 6.51, 7.05 and 6.89 mcg/mL, respectively.
When confounding factors such as age, smoking status and BMI were adjusted for, adiponectin levels were still positively associated with coffee consumption. There was a significant dose-response relationship between coffee consumption and adiponectin levels. However, there were no significant differences in adiponectin levels between those who drank 1–2 cups and those who drank >2 cups per day.
Green tea was not associated with adiponectin levels. There was also no association between coffee consumption and total cholesterol, HDL or LDL.
Although this study included only men, similar findings have been reported in women. In one study, diabetic and non-diabetic women who drank at least four cups of coffee per day had higher adiponectin levels than those who didn't drink coffee regularly (link). Interestingly, caffeine consumption was also associated with adiponectin levels. Perhaps the adiponectin-increasing effect of caffeine is diminished or blocked by other compounds such as L-theanine in green tea.
There's also one interventional study on habitual coffee drinkers that found coffee consumption increased adiponectin levels (link). Unlike in the study on Japanese males, total cholesterol and HDL also increased – possibly because the intake of coffee was higher (8 cups per day) at the end of the experiment.
Based on this and other studies, the key points are:
a) those who drink coffee have higher adiponectin levels than those who don't
b) those who have higher adiponectin levels have lower body fat percentage
All in all, while correlation does not prove causation, it seems plausible that drinking coffee could help maintain a lower body fat percentage and avoid type II diabetes and metabolic syndrome.
If you have personal experiences with coffee and weight loss, feel free to share them in the comment section below. For more information on weight and fat loss, see these posts:
Why Are Thin People Not Fat?
A Year of Intermittent Fasting: ADF, Condensed Eating Window, Weight Loss, And More
Green Tea and Capsaicin Reduce Hunger and Calorie Intake
The Twinkie Diet: Thoughts on Weight Loss and Cholesterol