Acute effects of a weight loss supplement on resting metabolic rate and anaerobic exercise performance
AbstractIn response to the increasing incidence of obesity, a large number of weight loss supplements (WLS) have become available that proclaim to stimulate weight loss and perceived energy. The purpose of the study was to examine a WLS containing caffeine blended with herbal extracts to
elucidate the effects of the WLS on resting metabolic rate (RMR), respiratory exchange ratio (RER), heart rate (HR), blood pressure (BP) and anaerobic exercise performance. Ten active, healthy males on an ad libitum diet were recruited for and completed the study using a randomised, double-blind, placebo-controlled, crossover method. Following baseline testing, with at least 24 hours between trials and after a 10-hour fast, subjects were tested on separate days one hour after taking either a placebo, morning WLS, afternoon WLS or evening WLS capsule for RMR, RER, HR, BP and anaerobic exercise performance as measured by a 30-second Wingate cycle ergometer test. There were no significant (p > 0.05) differences found in RMR, RER, HR, BP, absolute peak anaerobic power, relative peak anaerobic power or minimum absolute peak anaerobic power and fatigue index during the Wingate cycle ergometer test
between placebo, morning, afternoon or evening trials. No significant difference was found in the blood lactate concentrations. However, the morning WLS trial induced a greater increase in blood lactate concentration than the other trials (p < 0.05). Despite containing stimulatory
components, the results indicated that the WLS would not stimulate marked weight loss or perceived energy. The lack of effects could be due to an inadequate dosage of the stimulant, or a counteractive effect caused by the proprietary blend of ingredients. The study suggests that the
proclaimed effects of other weight loss supplements should also be scrutinised in order to determine their health implications and empirically assess their purported beneficial effects on wellbeing.
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