Green Tea, Exercise & Fat Oxidation

Most people, even those not sporting any formal qualifications in the field of medicine would have heard of catechins. While these antioxidants can be found in a range of foods including berries and in cocoa products (i.e. chocolate), the class of catechin thought to be most pharmacologically active (EGCG) is found in the greatest concentration in the leaves of the camellia sinensis plant (a.k.a. green tea).

So, why do scientists seem to pay such close attention to green tea in their studies? The short answer is that tea catechins are under constant examination due to the strong association of tea with long life and health in many ancient cultures.

However, green tea extract has also been found to improve exercise performance, increase fat oxidation and prevent obesity in animal models. These effects will be noteworthy to not only individuals seeking to attain favourable body composition, but those struggling with obesity or insulin issues.

The Study At Hand ...

Most studies with green tea have been performed in animal models. As such, it was a refreshing change to see researchers at the University of Birmingham investigate the effects of green tea extract ingestion on fat oxidation and glucose tolerance in humans.

What exercise aficionado's will find of interest is that the study assessed green tea's effects on these factors during moderate-intensity exercise.

Before I 'reveal' the study's conclusions, let me point out some points on methodology for the reader to consider ...

Methodological Notes:

• Each participant completed 30 minutes of cycling exercise at 50% of their VO2 Max which, by no means, would be considered 'strenuous'. 

• Moreover, the Green Tea Extract (GTE) used in the study contained a standardized extract 340mg polyphenols and 136mg EGCG and were ingested in the morning, around 1 hour before the bout of exercise. 

• In terms of body composition, the participants had an average BMI of 23.9 (which tells us simply that they weren't considered 'obese' by this standard). However, no mention was made about actual fat to muscle mass ratios, etc. Thus, it is difficult to say anything except that these participants represented your 'average joes' of society.

The Good Part:

The results of the study showed that green tea extract increased whole-body fat oxidation compared to the placebo. In addition, the participants used an extra 5% fat in their energy expenditure during exercise after taking the supplement.

The study also showed that GTE ingestion increased insulin sensitivity by 13% and reduced the insulin response to a glucose load by 15%, which is promising news for Type II diabetics and those with insulin resistance.

Real World Applications:

From the results of this study, and others of similar nature, it would appear that supplementing with green tea extract can increase fat oxidation (fat burning), increase insulin sensitivity and improve glucose tolerance. 

HOWEVER

Let me be frank in clarifying the fact that green tea is by no means a 'magic bullet'. Individuals will still have to adhere to a sensible diet and exercise regime in order to see it's effects on body composition. Nevertheless, the results are promising, particularly for those who DO require that extra 5% fat oxidation in order to achieve specific goals (e.g. competing bodybuilders).

For those seeking the extra boost, a good starting point is the methodological protocol identified by Venables et al. (2008) in their study. The extract, taken 1 hour prior to exercise should help with all of the issues highlighted, and ideally allow you to reap the benefits of this successful human trial.

Reference:

Venables, M. C., Hulston, C. J., Cox, H. R., Jeukendrup, A. E. (2008). Green tea extract ingestion, fat oxidation, and glucose tolerance in healthy humans. The American Journal of Clinical Nutrition, 87: 778-784.