can caffeine help me lose weight?

It is thought that caffeine was discovered in Ethiopia. It comes from many different sources including coffee, tea, chocolate, sodas, protein bars, medication and pre-workout supplements. It is consumed by millions of people everyday in its various forms. A lot of people need their coffee shot just to feel “normal”, while others say they could not live without their morning coffee.

Caffeine is absorbed through the stomach, processed in the liver and excreted via the kidneys. It peaks in blood between 15 minutes and 2 hours depending on body size, age, health status and tolerance and it has a half-life of 3 to 7 hours. A safe amount to consume for the average person is between 300-400mg’s (around 3 cups) per day.


Caffeine is an alkaloid compound (organic nitrogenous compound containing nitrogen atoms) that has physiological effects on humans, especially the central nervous system. Caffeine can temporarily relieve tiredness and increase alertness and also increase energy to working muscles increasing their work capacity.

Adenosine is a purine nucleoside attached to a ribose sugar molecule moiety, and is the reason we need our coffee shot. In the brain adenosine is an inhibitory neurotransmitter and acts as a central nervous system depressant, promoting sleep and decreasing arousal. It also plays roles within the heart, lungs, liver, kidneys and in energy production. Adenosine binds to adenosine receptors in the brain, causing drowsiness by slowing down nerve cell activity, blood vessels dilate, most likely to let more oxygen in during sleep.

So now we know why we get tired, how does caffeine help?

Caffeine binds to adenosine receptors, blocking their affects, preventing the slow down that would be caused by adenosine. As a result, the cell can no longer identify adenosine because caffeine is taking up all the receptors that adenosine would normally bind to. Instead of slowing down the nerve cells speed up. Caffeine also causes the brain's blood vessels to constrict, because it blocks adenosine's ability to open them up. This effect is why some headache medicines like Anacin contain caffeine, if you have a vascular headache, the caffeine will close down the blood vessels and relieve it.

You now have increased neurons firing in the brain. The pituitary gland sees all of this activity and thinks some sort of emergency must be occurring, so it releases hormones that tell the adrenal glands to produce adrenaline. Adrenaline is the "fight or flight" hormone, and it has a number of effects on your body:

  • Your pupils dilate

  • Your breathing tubes open up (this is why people suffering from severe asthma attacks are sometimes injected with adrenaline)

  • Your heart beats faster (you should be cautious about consuming caffeine if you have a heart condition, as caffeine increases heart rate).

  • Blood vessels on the surface constrict to slow blood flow from cuts and also to increase blood flow to muscles

  • Blood pressure rises (caffeine increases adrenaline, which reduces hormones that naturally open arteries and this increases blood pressure).

  • Blood flow to the stomach slows

  • The liver releases sugar into the bloodstream for extra energy

  • Muscles tighten up, ready for action

This explains why, after consuming a big cup of coffee, your hands get cold, your muscles tense up, it makes you feel excited and can feel your heart beat increase.

In the short term there will also be an increase in the catabolic hormone cortisol. Cortisol is linked with increased fat around the middle, immune system suppression, decreased testosterone (needed to build muscle, burn fat and increase metabolism), osteoporosis and fluid retention to name a few.

Drinking a lot of caffeine chronically can make you insensitive to adrenaline, making you need more stimulants to feel normal. The net result of long-term use is adrenal exhaustion, causing low cortisol and DHEA. This overuse of the adrenals will also have a knock on affect on the thyroid and sex hormones; good thyroid function is essential for metabolism and therefore weight management.  

Caffeine is acidic and can cause heartburn, upset stomach and ulcers. High caffeine consumption can cause anxiety, nervousness, insomnia, stomach upsets and (it is thought) contribute to the exacerbation of inflammatory conditions such as eczema. In rare cases of caffeine overdose, hallucinations, confusion, vomiting and even death have been seen.

A few studies indicate that drinking coffee or tea with caffeine may slightly boost weight loss or prevent weight gain, but there's no evidence that increased caffeine consumption results in significant or permanent weight loss. Plus some of the studies looking at caffeine and weight were of poor quality or used animals, which makes the results questionable.

Theories about how caffeine affects weight

Appetite suppression - caffeine may reduce your desire to eat for a brief time.
Calorie burning - caffeine may stimulate thermogenesis (heat generated and subsequently calories burnt from food digestion), but this probably isn't enough to produce significant weight loss.
Water loss - caffeine acts as a diuretic, which means it increases the amount of urine you excrete. This water loss may temporarily decrease your body weight.

While it may be tempting to try caffeine to aid weight loss, keep in mind that caffeine's a stimulant and too much can cause nervousness, insomnia and other problems. It is now thought that caffeine can actually contribute to weight gain as some caffeinated beverages, such as specialty coffees, are high in calories and fat and studies have shown that caffeine contributes to insulin resistance (thus making it harder to lose weight, see bottom of article for insulin resistance), increases appetite (again making it harder to lose weight) and contributes to food cravings (making it difficult to adhere to a weight loss diet). In those studies, even decaffeinated coffee is shown to be detrimental to weight loss.  The increase in the already mentioned stress hormones are also linked to stress eating, the inevitable drop in blood sugar after caffeine cause cravings and the increase in cortisol interferes with the appetite controlling hormones leptin and ghrelin. If caffeine is consumed above a person’s tolerance, stress hormones such as cortisol are released increasing fat deposits around the middle.

Many overweight people, particularly those who have frequently dieted and lost weight only to regain it later, may be insulin resistant. Unfortunately, many people who are insulin resistant are unaware of it. Caffeine contains chlorogenic acid, which is linked to insulin resistance, further affecting your metabolism.

In the long term, avoiding caffeine will help to boost your metabolism. Naturally increasing your metabolism by combining correct eating and cardio exercise and weight training will lead to fat loss and increased lean muscle. Lean muscle is your metabolic furnace that will burn extra calories/energy 24 hours daily and not just when you are exercising.

If our bodies are in a stressed state for extended periods of time, like when you have too much work to do, are late for a meeting or you are stuck in a traffic jam, it's like pressing your foot down on an accelerator while the hand break is on and the car is in neutral. The adrenaline that is produced during these stressed out periods is also produced when drinking caffeine.

GABA (gamma-aminobutyric acid), functions as an inhibitory neurotransmitter in the brain that directly affects the personality and the capability to manage stress. If you struggle to fall asleep or stay asleep, GABA can help you sleep better because it aids in the relaxation of the brain. Caffeine interferes with GABA and prevents it from having its calming affect. This then increases physiological and psychological stress (often associated with both overeating and difficulty adhering to a weight loss diet).

Long- term stress is associated with irritable bowel syndrome (IBS) and other digestive problems due to blood flow being diverted away from the digestive system. It also increases blood thickness and blood pressure that may lead to cardiovascular problems. Caffeine is also acid forming, which can contribute to digestive issues such as IBS. Caffeine can aid movement of digestion, though conversely too much can cause diarrhea.

Another side effect of consuming too much caffeine is frequent urination. This can cause the body to become quite easily and quickly depleted of some of the nutrients essential for maintaining good health. Minerals that can become depleted include calcium, magnesium, sodium, phosphate and potassium.

Caffeine can reduce mineral absorption by up to 80 percent. Caffeine is thought to inhibit the absorption of iron and some of the A and B vitamins. Iron is an essential part of the diet and needed for red blood cell production and function, for muscles and the immune system.

Calcium deficiency due to loss and poor absorption can affect bone density. Poor nutrient absorption can lead to a number of ailments, such as osteoporosis, anaemia, arthritis, diarrhea, acne, dry eyes and poor energy production. Acidity produced from over consumption of caffeine will contribute to the alkaline mineral calcium being taken from bone to help buffer the acidity. 

Due to the effects caffeine may have on hormones there have been studies that show links between over consumption of caffeine and an inability to become pregnant. This is due to hormone disruption, especially the hormone oestrogen. If a woman is older or a man already has suboptimal sperm levels, reducing caffeine is recommended. Once pregnant, caffeine can cross placenta into the womb, increasing the baby’s heart rate and metabolism. Is has also been seen that caffeine slows fetal growth increasing the risk of miscarriage.

Caffeine withdrawal increases irritability, drowsiness, headaches, tremors (in some) and dehydration.

What is insulin resistance?

Normally, food is absorbed into the bloodstream in the form of sugars such as glucose and other basic substances. The increase in sugar in the bloodstream signals the pancreas to increase the secretion of a hormone called insulin. This hormone attaches to cells, aiding the removal of sugar from the bloodstream helping them enter inside the cells so they can be used for energy.

In insulin resistance, the body's cells have a diminished ability to respond to the action of the insulin hormone. The pancreas then increases its insulin secretion to compensate. High levels of insulin and sugar in the blood are a marker for insulin resistance.

So from a weight loss standpoint caffeine may not be the answer. There is evidence to suggest that consumption of caffeine has beneficial affects on Alzheimer’s, enhanced athletic performance and, in the short-term, increased concentration.

Does caffeine enhance performance?

A lot of ergogenic aids that are thought to enhance performance contain caffeine. It is easy to see why it is used when you know what affects it has on the body. Benefits include increased mental alertness, concentration, decision-making ability, endurance capacity, time to fatigue, fatty acid metabolism, strength and power.

It is thought that the adenosine receptor antagonism is the primary mode for the increase in performance. This has been shown in many studies from cycling (endurance) to strength training.

In terms of quantity, 5mg per kg of body weight is the safest predictable amount of caffeine. At this levels urine caffeine concentrations will be under the doping limit of the international Olympic committee. Taking more than this appears to have no additional benefit, although there is an increase in side effects. Like any nutrient (macro or micro), too much can be toxic to the body, so make sure you take the correct dose. 

Caffeine improves performance, but only for a short time!

There are many studies showing that consuming a caffeine rich product before training has a beneficial effect on performance. This is very true but the human body is also very good at adapting quickly. This is why it’s so important to change your exercise routine up to prevent a plateau. The thing with coffee is that the amount you need on day one to give you a boost will not be enough on day thirty. Caffeine blocks the neurotransmitter adenosine (which makes us sleepy) by attaching to the receptor, which stops us feeling tired. There are a few different types of these receptors however and they have differing effects. There is a type 2 adenosine receptor whose job is to prevent dopamine acting too strongly. Caffeine blocks this receptor, causing an increase in dopamine activity. Dopamine is associated with desire, motor control, motivation, emotion, endocrine regulation, food intake and more. So little increases in dopamine can make us feel good, however chronic high levels of dopamine in the brain synapses can be dangerous. So a safety mechanism kicks in and the cells down regulate their sensitivity to dopamine becoming less sensitive and reducing its effects. This will naturally reduce the positive mood, motivation and ergogenic effects over time. So to get that original effect from day one we need to consume more caffeine to get that boost. My tip is to cycle your caffeine intake, one month on one month off. Choose when your training period needs the boost the most; that last month of fat loss leading to a competition or holiday for example.

On a more serious note, high dopamine levels created from an abuse of substances (cocaine, methamphetamines) that increase dopamine are linked with conditions such as schizophrenia and Parkinson’s disease. Caffeine in moderation is acceptable, however those who consume large amounts over a long time should be aware of the possible damage.

Caffeine & your hormones

As mentioned in the caffeine and weight loss section above, caffeine has a massive impact on our hormones. Hormones work synergistically and need to be in balance. Cortisol is released after caffeine is consumed. Cortisol is released first thing in the morning and during exercise, so if exercise already increases cortisol release, and caffeine has been shown to increase performance by an increase in the central nervous system drive and an increase in cortisol release, it may be a good idea to use caffeine pre-training. The cortisol release post caffeine should be avoided throughout the rest of the day due to the negative cascade that takes place with high cortisol levels.  

It is worth remembering that 50% of caffeine stays in your system for five to six hours after consumption (half life). So if you need your caffeine to get you through a workout and you workout in the evening it is worth noting that the caffeine may disturb sleep, which will then have a negative effect on results. The healthier your diet and detoxifying processes the quicker this is removed.

Your coffee can increase damaging toxins

There are two phases of liver detoxification, phase one and phase two. Phase one is known as P450 phase detoxification. Heavy metals and chemicals from the air, water and food enter phase one and are then converted by the P450 enzyme into even more toxic chemicals than they originally were. These toxins now enter phase two detoxification before they do too much damage. Caffeine speeds up phase one detoxification. If phase two is not running as fast there could be a build up of intermediary toxins which can cause free radical damage. If you can drink lots of coffee without it affecting you, this could be a sign that your phase one detox is overactive, running too fast and contributing to a build up of toxins. The body’s way of dealing with too many toxins is to push them into fat cells. Some believe that new fat cells (adipocytes) are produced them to deal with this, while others think that we only produced during childhood. We do not actually lose fat cells, they shrink or grow depending on lifestyle, diet and activity.

Like any stimulant, your body will gradually get used to the caffeine, which means you will need to consume more to get the same affect. It may be a good idea in this case to consume caffeine periodically on a month on month off basis to prevent a plateauing affect.   

Of course there are side effects to over consumption of caffeine (irritability, anxiety, restlessness, headaches, insomnia, twitching, rapid or irregular heart beat, nausea, vomiting, increased breathing rate), so it’s best used with caution.   

Caffeine alternatives

Beyond coffee and tea caffeine is found in a variety of food and drinks. These include chocolate, coffee flavoured ice-cream, cola drinks, Lucozade, the herb guarana and some pain killers. 

Coffee beans contain 1 to 2 percent caffeine. Tea contains a chemical called theophylline, which is actively more potent containing 3 to 4 percent caffeine in the leaves. However, when the tealeaves are brewed more caffeine is extracted, which is why coffee is higher in caffeine than tea.

Decaffeinated coffee has 97 percent of caffeine removed. However, coffee beans vary greatly in strength, and 3 percent of some beans can still contain a significant amount for some people, depending on their individual tolerance. There have been studies that show the decaffeinated coffee of some well known coffee brands contain as much as 32mg of caffeine.

The following table shows amounts of caffeine in a variety of products.

Food / Drink Caffeine (mg)
Decaffeinated coffee (1 cup) 2 - 9
Instant coffee (1 cup) 60 - 80
Drip brewed coffee (1 cup) 90 - 150
Tea (1 cup) 30 - 70
Cocoa (1 cup) 55
Portion of coffee flavoured ice cream 40
1 oz milk chocolate 15
1 oz plain chocolate 35
Painkiller (per tablet) 32-100
Starbucks Venti Americano 300
Diet coke (330 ml can) 42

Caffeine free coffee alternatives

  • Bambu - made from chicory, figs, wheat, malted barley and acorns.

  • Barleycup - made from roasted barley, rye and chicory.

  • Caro - made from roasted malted barley, chicory and rye.

  • No Caf - made from barley, malt, chicory, rye and figs.

  • Cotswold Dandelion coffee – made from roasted dandelion root.

  • Prewetts instant chicory – made from roasted root of chicory plant.

  • Soyfee - made from soya beans.

  • Teecino – made from carob, barley, chicory, dates, figs and almonds.

Caffeine free tea alternatives

  • Fruit infusions come in a variety of flavours including blackcurrant, chamomile, cranberry with raspberry and elderflower, Echinacea and raspberry, elderflower with strawberry and rose, lemon and ginger, mandarin and lychee, orange with mango and cinnamon, peach and passionfruit, pear and guava, camomile, peppermint, raspberry with strawberry and loganberry, strawberry and mango, and wild blackberry with nettle.

  • Red Bush (Rooibosch) tea

  • Dr. Stuarts Botanical teas

  • Clipper dandelion leaf tea

  • Yogi teas

  • Celestial seasonings tea – made from blackberry leaves, roasted chicory root, hawthorn berries, beet root, natural tea flavour, and hibiscus flowers.

  • Honeybush tea

Yet it’s not all bad news

On a positive note for coffee drinkers, research carried out on half a million European people has shown that those who drink three cups of coffee live longer than those who don’t, especially those with circulatory and digestive diseases. A study of 180,000 people across America displayed similar results. The study showed a 12% decrease in mortality for those who drink 1 coffee per day and an 18% decrease in those who drank 3 cups. Drinking coffee appears to reduce inflammation, lower insulin resistance and the antioxidants play a role in preventing cancer. Research has also seen benefits in coffee consumption and diabetes, depression and Parkinson disease. Plus studies have also shown that regular coffee consumers (not decaf) have a lower risk of Alzheimer’s and dementia.

Coffee, black and green tea are high in antioxidants and other protective phenolics (tannins), compounds that play an important role in both artery damage and cancer prevention.

Make up your own mind….., but remember, if you do still choose to have caffeine, it's best not to consume any after midday.

This article has
been written by
Terry Fairclough