By Matt O'Neill, MSc(Nut&Diet), APD
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It's often claimed that caffeine enhances fat burning. But does it really work this way and is it worth recommending as part of a fat loss program?
Caffeine has been consumed by humans in one form or another for thousands of years. For many of us, a good coffee is a daily ritual. And in recent times caffeine has found its way into energy drinks, snack bars and slimming pills. All of these products may be worth taking as part of a fat loss program for a number of reasons.
Increased energy expenditure
Energy expenditure tends to become elevated with doses of caffeine. It has been estimated that the habitual consumption of 6 cups coffee (i.e. 600 mg caffeine/day) causes and increase in energy expenditure of about 100 calories a day.
The energy cost (thermogenic effect) of digesting and processing food has also been found to be higher when caffeine has been taken.
Two main mechanisms appear to cause the energy burning boost. Firstly, sympathetic nervous stimulation has a direct effect on muscle energy production. Secondly, caffeine-induced elevation of epinephrine can have an indirect affect on muscle activation. Both these mechanisms show how some people can experience fidgeting, jitters and hand shakes after drinking coffee.
Caffeine may also increase blood pressure in some people and so increase the energy cost of cardiovascular output. However, this effect appears to diminish over time.
Greater fat burning
Caffeine has been found to cause greater lipolysis (body fat breakdown) and fat oxidation (fat burning for fuel) in a number of studies. Although we're a long way off being certain, scientists think caffeine boosts the human energy burning processes that use fat for fuel.
Enhanced exercise performance
A significant number of research papers reveal caffeine's ergogenic impact on exercise output. It has increased both endurance performance and shorter duration strength challenges.
If individuals are able to train harder with caffeine, then fitness gains will come faster and subsequent training sessions will deliver a greater calorie output.
Responders and nonresponders
The library of research on caffeine is cluttered with mixed results. You'll find studies showing large positive effect on the fat loss parameters discussed. You'll also find studies with no effects. This is explained by categorising people as responders and nonresponders. Some people are very senstive to caffeine and others are seemingly immune to it.
This means that caffeine may have a potent benefit for fat loss in some individuals but be wasted on others. Monitoring the personal response to caffeine will be important to evaluate its merits.
Minor thermogenic effects may be present with as little as 50mg caffeine per day for some people. Athletes who take caffeine for its ergogenic effect may consume 300-500 mg one hour before an event.
The caffeine content of beverages varies considerably, making it hard to know your level of intake. Typically, a perculated, drip or filtered coffee will contain about 85 mg caffeine. Instant coffee has less at around 60 mg. Tea and cola drinks will provide about 40 - 50 mg. Energy drinks can have around 80 mg and some super-sized takeaway coffees can pack over 500 mg caffeine.
Something else in coffee
Non-caffeine chemicals in coffee may also provide benefits. For example, chlorogenic acid found in coffee may slow glucose absoption in the gastrointestinal tract and reduce the risk of type two diabetes.
Any down sides?
Caffeine consumption will cause problems for some people, especially those who are hyper-responsive to its negative affects. Some people may experience caffeine-induced hypertension. Caffeine may also interact adversely with some medications.
A higher coffee intake has also been linked with accelerated bone loss in postmenopausal women who fail to reach a daily target of 800mg calcium. An extra cup of skimmed milk for every coffee is a practical way to address this issue.
Pregnant women who consume higher levels of caffeine may be at a greater risk of miscarriage or give birth to an underweight baby.
Caffeine does have a diuretic affect, but because coffee and cola drinks provide a significant source of fluid in many diets, caffeine is unlikely to cause dehydration - particularly in habitual caffeine consumers.
- Caffeine intake can be a useful fat loss or body weight maintenance strategy for those who respond to its effects.
- Introducing caffeine to those who do not habitually consume it may have the greatest effect.
- Habitual caffeine consumers may already have achieved a ceiling of benefits and be non-responsive to additional caffeine.
- For most people, a caffeine intake up to 4-5 cups of instant coffee (250 - 300 mg) will not pose major health risks.
- Finally, keep in mind that the fat loss benefits of caffeine will be relatively minor compared to significant positive changes to diet and exercise habits.
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