Caffeine and coffee: their influence on metabolic rate and substrate utilization in normal weight and obese individuals

Abstract

A series of four trials was carried out to investigate the effects of caffeine and coffee on the metabolic rate and substrate utilization in normal weight and obese individuals. In the first trial 8 mg/kg caffeine was compared with a placebo in normal weight subjects. Metabolic rate increased significantly during the 3 hr after caffeine ingestion. While plasma glucose, insulin, and carbohydrate oxidation did not change significantly, plasma free fatty acid levels rose from 432 +/- 31 to 848 +/- 135 muEq/liter and were accompanied by significant increases in fat oxidation during the last hour of the test. In the second and third trials the effects of coffee providing 4 mg/kg caffeine were studied in control and obese subjects. Metabolic rate increased significantly in both groups; however, significant increases in fat oxidation were only observed in the control group. Plasma free fatty acids did not change in the obese. In the fourth trial, coffee was taken with a 3080 kJ meal. The thermic effect of the meal was significantly greater after coffee than after decaffeinated coffee and again fat oxidation was significantly greater after coffee. In conclusion caffeine/coffee stimulates the metabolic rate in both control and obese individuals; however, this is accompanied by greater oxidation of fat in normal weight subjects.

Metabolic and physiological effects of ingesting extracts of bitter orange, green tea and guarana at rest and during treadmill walking in overweight males

“…The increases in energy expenditure in these studies were attributed to greater lipid oxidation with or without any increase in CHO oxidation. Acheson et al 22 observed a significantly increased metabolic rate following caffeine ingestion (4 and 8 mg kg À1 ) in subjects of normal weight, which was accounted for by greater lipid oxidation, although they showed a reduced effect on fat oxidation in obese subjects. Similarly, Colker et al 23 showed an average daily increase of 2-3% in basal Effects of bitter orange, green tea and guarana C Sale et al metabolic rate following the ingestion of 975 mg of citrus aurantium and 528 mg of caffeine when compared to both placebo and control conditions.…”

The effect of caffeine on energy balance

“…Numerous studies described the beneficial effect of caffeine on EE [4,[6][7][8][9][10][11][47][48][49][50]. Two studies examined the influence of caffeine on the RMR in young (20-40 years) physically trained and untrained men.…”

“…Several studies investigated whether the beneficial effects of caffeine on EE are related to body weight [6][7][8][9][10]. Previous studies have found that the pharmacokinetics of caffeine is different between lean and obese subjects [7,[51][52][53].…”

“…Previous research found that the adipose tissue of obese rats had a reduced capillary density and a slower flow rate through the capillaries in comparison to the adipose tissue of lean rats. Other studies reported that the FFA response to caffeine in resting obese humans was delayed [6,51], probably as a result of a decrease in the rate of caffeine delivery to the adipose tissue, which leads to a decreased sensitivity to lipolysis stimuli. These results support the finding of other studies [7,53] that obesity results in modifications in regional blood flow and thus in the distribution and clearance of some drugs.…”

“…Acheson et al [6] investigated the effects of coffee (~ 4 mg/kg caffeine) on the metabolic rate and substrate utilization in LW (n = 7) and OW (n = 6) individuals (gender was not specified). Resting metabolic rate increased significantly in LW (12% ± 3%, p < 0.01) and in OW (10% ± 2%, p < 0.05), with no significant difference between the groups.…”