Variation in the Impact of Coffee on the Metabolic Rate

The investigators will study the variation in the impact of coffee on metabolic rate and investigate the impacts of age, sex, body composition and regularity of habitual coffee consumption on this effect. The investigators will recruit healthy participants, half male and half female. Participants will be required to perform no strenuous exercise for 14 hours and no moderate of vigorous exercise for 2 hours before the measurements. When the participants arrive at the lab on the day of the experiment, they will sign an informed consent form, a health history questionnaire and a daily coffee consumption questionnaire. Participants will be randomly allocated into 3 groups and given 180mls of coffee to consume containing 100, 200 or 300 mg of caffeine. A fourth group will be dosed with 100 mg of caffeine containing 13C uniform labelled caffeine to trace the pattern of caffeine degradation via the appearance of 13CO2 in the breath and labelled compounds in the urine. The primary outcome is the change in resting metabolic rate from before and after coffee drinking. Secondary outcome measures are heart rate, electrocardiogram, blood pressure, body temperature which will be measured before and after the coffee consumption. Professional nurses will take 8ml of venous blood from all participants as genotyping blood samples. Genomic DNA will be extracted from whole blood samples and analysed for single nucleotide polymorphisms (SNPS).

Inclusion criteria

Healthy adults 18-40 years old

Exclusion criteria

Those who have undergone surgery in the past 6 months. People are requiring long-term medication. People have metabolic diseases, like diabetes, hypoglycemia, gout, osteoporosis, etc.

People have digestive diseases, like gastric ulcer, pancreatitis, intestinal obstruction, etc.

Those who have recently lost weight for various medical reasons ( like cancer, etc.).

People are suffering from infectious diseases ( like HIV, etc.). People have blood phobia, pathological hypo or hyper tension. People with impaired glucose tolerance. Those who are afflicted with claustrophobia.