Why is it so difficult to be healthy? Why is life made so difficult by the conflicting messages we are constantly given about food, drink and supplements? One minute we are told to reduce the amount of coffee we drink, the next minute we are told to take caffeine tablets to increase weight loss. What is the truth about caffeine and weight loss?
Caffeine is a naturally occurring chemical stimulant that is found in variable quantities in the beans, leaves, and fruit of some plants. The way it acts as a stimulant is via the central nervous system (CNS)and its use normally results in the user feeling alert and energised, an effect many students will testify to whilst simultaneously cramming for university finals whilst drinking a double espresso. Another commonly quoted effect of caffeine ingestion is weight loss. Considering that caffeine is a CNS stimulant it would seem to make sense that it could act as a weight loss agent, doesn’t it? There are a number of long term studies that suggest caffeine intake is linked to a reduction in weight gain and this seems to be due to a number of factors based on the chemistry of the caffeine molecule.
Thermogenic effects of caffeine
Caffeine levels tend to peak within an hour of ingestion, which tends to be when people start to feel the first stimulant based effects. It would seem that caffeine can increase energy expenditure by approximately 10% through increasing heat production in the body. This thermogenic property of caffeine is thought to be one of the major routes leading to an increased rate of daily energy expenditure (Riedel et al., 2012). In quantitative terms ingesting 600mg of caffeine has been shown to result in an increased expenditure of approximately 150kcal/day (Dulloo et al., 1989). It has to be noted that if you are a habitual coffee drinker, or if you frequently use caffeine tablets as part of you supplement regime, you will not see the same thermogenic effects as a first time user.
It is frequently suggested that the consumption of caffeine is followed by an increase in lipid oxidation (Bracco et al., 1995). Although it is an almost non-disputed fact that caffeine mobilises fatty acids from adipose tissue, studies have found very little evidence to support the notion that any performance enhancing effect is the result of fat oxidation (Graham et al., 2008). The fact that caffeine can mobilise fatty acids is a very important property as it is thought to have a muscle-glycogen sparing effect. What this essentially means is that you will still have glycogen reserves left and ready to be used during the latter stages of training.
The mobilisation of fatty acids from fat stores enables free access to fats for use as energy rather than glycogen and muscle tissue. Caffeine can activate this pathway due to one surprising property; it stimulates the pancreas to produce a small volume of insulin. How can it elicit such a response when it is neither a carbohydrate nor a protein and contains no calories? Well it all relies on caffeine?s ability to enhance the production of the hormones Adrenaline and Glucagon, which are responsible for the release of glycogen from the liver and energy from fat stores. In turn this results in higher blood sugar and elevated insulin and decreased insulin sensitivity. On closer investigation we can see that the caffeine induced decreased insulin sensitivity is due to the increase in free circulating fatty acids, which are now available as energy for the body. The agent that promotes the breakdown of adipose tissue is one of caffeine’s metabolites – paraxanthine.
If your aim is to target stubborn fat then the best piece of advice would be to ingest caffeine prior to your workout, preferably on an empty stomach. A relatively recent study has shown that taking caffeine pre workout can boost your fat burning potential by about 30% throughout the duration of your workout (Spriet, 1995). Interestingly enough, studies have shown that the fat burning effect can even extend beyond the workout itself by utilising what is often referred to as the afterburner effect. It is important to drink plenty of water during your workout as caffeine is also a diuretic.
Being a stimulant, caffeine increases both the heart rate and blood pressure resulting in an increased volume of blood. This blood of course has to be filtered by the renal system and the result is an increase in the volume of waste produced. The result, as many coffee drinkers will have experienced, is more frequent urination. This acute diuretic effect is only experienced with large doses of caffeine typically above 250mg, and is rarely experienced in the lower levels of caffeine consumed in single cups of coffee or tea. As with any stimulant you will also find that regular use results in the body becoming habituated to the effects of caffeine. Can this diuretic effect contribute to weight loss? The answer is that although there may be a small change on the scales, any loss of water should never be regarded as effective weight loss.
Lopez-Garcia E, van Dam RM, Rajpathak S, Willett WC, Manson JE, Hu FB. Changes in caffeine intake and long-term weight change in men and women. Am J Clin Nutr 2006;83:674?80.
Riedel A, Pignitter M, Hochkogler CM, Rohm B, Walker J, Bytof G, Lantz I, Somoza V. (2012) Caffeine dose-dependently induces thermogenesis but restores ATP in HepG2 cells in culture. Food Funct. 2012 Sep;3(9):955-64. doi: 10.1039/c2fo30053b. Epub 2012 Jun 19.
Dulloo A, Geissler C, Horton T, Miller D. Normal cafeine consumption: influence on thermogenesis and daily energy expenditure in lean and postobese human volunteers. Am J Clin Nutr 1989;49:44?50.
Graham et al., 2008 Appl Physiol Nutr Metab. 2008 Dec;33(6):1311-8. doi: 10.1139/H08-129