How does caffeine react to the human body, is it safe to get rid of excess weight? Or useless?
In this page, we explain a relationship between weight loss and the caffeine effects on the body. Let’s figure out!
As we know, Caffeine is one of the most commonly used ingredients in fat loss supplements.
This occurs naturally in leaves, seeds, or fruit from more than 60 different plants including cola, mate leaves, and guarana paste. It is commonly found in coffee and chocolate and is often used as a flavoring agent in cola beverages.
Exerts caffeine effects through a number of different mechanisms. The primary actions of caffeine are it stimulates the central nervous system and amplifies lipolysis.
Lipolysis is controlled by an enzyme called hormonesensitive lipase (HSL). This enzyme exists in an inactive and active form.
To activate HSL, another enzyme, adenylate cyclase, converts ATP into cyclic-3′, 5′-AMP (cAMP) Cyclic-AMP. After that activates cAMP-dependent protein kinase which in turn phosphorylates HSL, thus activating the enzyme.
The active form of the enzyme is responsible for cleaving the FFA off of the glycerol backbone of the triacylglycerol molecule.
The FFA is then released into the bloodstream. Lipolysis ceases when cAMP is degraded to 5′ AMP by phosphodiesterase, thus becoming inactivated.
So, it makes sense that any process that maintains cAMP levels will prolong the life of the HSL active form and consequently lipolysis.
Caffeine and other methylxanthines inhibit phosphodiesterase activity. Caffeine is thus able to prolong the responses of cAMP by slowing the degradation of this messenger.
Therefore, lipolysis continues for a longer period of time resulting in more FFAs being released into the bloodstream.
Several studies have been conducted on animals and humans about the effectiveness of caffeine.
In Vitro Studies
Studies in Vitro allow scientists to figure out the possible mechanism of action of certain substances on metabolism.
Research on caffeine, as discussed before, shows the caffeine inhibits phosphodiesterase activity. This leads to an increase in adipose tissue lipolysis, a catabolic process.
For a cell to carry on both catabolic and anabolic processes at the same time is difficult. The purpose of adipocytes is to store fat. The adipocyte can use fatty acids or glucose for triacylglycerol synthesis.
In the case of glucose, the cell must first convert the glucose into fat through a process called lipogenesis.
Yet, if lipolysis is going on, it is not possible for the cell to perform lipogenesis. Steinfelder and Petho-Schramm have demonstrated that caffeine inhibits glucose transport into rat adipocytes.
Also, it can be affecting adipose tissue, caffeine also affects brain tissue. Some of its effects in the brain will discuss in the section on adverse reactions. But, other caffeine effects in the brain may aid in the stimulation of lipolysis.
The anterior pituitary gland handles growth hormone (GH) production and secretion.
Growth hormone also stimulating glucose and amino acid uptake also stimulates lipolysis. Thus, GH can increase fatty acid oxidation.
In Vitro studies, cultured pituitary cells rats showed that caffeine stimulated GH secretion. This increase is more than likely caused by the inhibition of phosphodiesterase.
As in many cells, cAMP acts as a second messenger, which stimulates a number of metabolic pathways inside a cell. In this case, caffeine effects on phosphodiesterase result in an increase in GH secretion.
It remains to be determined whether the oral consumption of caffeine stimulates GH secretion in humans. If it does, whether the increase in GH is significant enough to alter lipolysis.
Some insight into this question will be provided when animal and human research is discussed.
When the HSL is working at cleaving the fatty acids off of the glycerol backbone. From triacylglycerol, the molecule is released into the circulation along with the three FFAs.
Although not related to lipid oxidation in the muscles! The body needs to do something with glycerol. This can enter glycolysis to function for oxidation or gluconeogenesis.
Beside stimulating lipolysis, caffeine also stimulates gluconeogenesis. The making of glucose in the liver.
As a test, Caffeine added to the suspensions of rat hepatocytes. It resulted in a two-fold increase in gluconeogenesis.
Furthermore, it is used to maintain blood sugar levels or act as a precursor for liver glycogen.
The affects of caffeine on growth hormone secretion in animals are not as clear as the in vitro work. Work from two different laboratories has produced conflicting results.
One lab has reported that caffeine injection results in a lowering of GH and thyroid hormones.
Another lab reported that GH levels were increased following a single injection of caffeine.
After 10 days of caffeine injection, GH levels were still elevated. But not to the extents that were observed following the initial injection.
The differences between the two studies could be attributed to the age of the rats used. Clozel et al. used 5-day-old rats while Spindel et al. used older rats. This lends support to human research showing an age caffeine effects.
In addition to affecting the growth hormone, Caffeine also affecting the Katekolamin release. This process is present in chromaffin details in the adrenal medulla.
Catecholamines can also stimulate lipolysis. Catecholamine biosynthesis begins with the amino acid tyrosine.
Tyrosine is hydroxylated to dopa by tyrosine hydroxylase. This is a rate-limiting enzyme in catecholamine biosynthesis. Tyrosine hydroxylase appears to be regulated by cAMP-dependent protein kinase.
Therefore, caffeine may have the same effects on catecholamine biosynthesis as it does on lipolysis. That is, caffeine may prolong the activity of tyrosine hydroxylase by inhibiting phosphodiesterase.
Furthermore, the release of catecholamines is calcium-dependent. Caffeine is able to increase intracellular calcium levels through the release of calcium from intracellular stores and by increasing the entry of calcium from extracellular stores.
Though the caffeine effects on hormones in animals are not all that clear, caffeine effects on lipolysis are clear. Numerous studies have reported that caffeine increases lipolysis in laboratory animals.
Furthermore, research shows that caffeine produces a faster fat mass loss in trained rats. And this is different compared to mice that do not receive caffeine but still do it.
Human Studies – Caffeine Effects on Body
Caffeine research in humans has produced some mixed results with positive results. This may depend on the age, sex, and weight of the subject, and also the prior use of caffeine by the subject.
The supplementation of caffeine effects on resting metabolic rate and thermogenesis have been studied. Included the lean, obese, post obese (following weight loss), and young and old.
Metabolic rate and/or thermogenesis increases with caffeine in all populations and its dosage. But, fat oxidation appears to increase only in lean individuals.
Obese and older adults seem to have a blunted response to caffeine on a rise in fat oxidation.
There could be many reasons why the lean and obese respond differently to caffeine. One reason could be the way caffeine is metabolized by the body.
Yet, Caraco reported that obesity minimally alters caffeine pharmacokinetics. This small alteration should not need any significant dosage modifications.
The differences among the populations may be due to the form in which caffeine was consumed. The studies that reported a difference between lean and obese individuals used coffee as the form of delivery.
In Graham et al report, there was a blunted Catecholamine response during exercise after coffee consumption. The results are very different when compared to consuming pure caffeine.
The study by Arciero that compares young and old men used pure caffeine. The other factor that could have influenced the results was the varying amount of caffeine used.
As in animals, caffeine also alters the plasma levels of certain hormones. Caffeine has repeatedly been shown to increase catecholamine levels. Furthermore, the increase in catecholamines appears to be dose-dependent.
More research was carried out with a single dose of caffeine (500 mg). It may also raise growth hormone and tri-iodothyronine (T3 ) in men, but not women.
As discussed above! The caffeine-associated increase in growth hormone could further increase lipolysis and fat oxidation.
Triiodothyronine is a thyroid hormone that increases the resting metabolic rate. It also amplifies the physiological signals responsible for stimulating lipolysis and fat mobilization.
Safety and Toxicity
Although it would appear that caffeine works well as a fat loss supplement, it has negative side effects. The Caffeine effects have been reported to elevate arterial blood pressure and heart rate.
Furthermore, it results in diuresis and increased gastric secretion. The latter of which can lead to loose bowels and possibly diarrhea at higher dosages.
Chronic caffeine ingestion is associated with a decrease in cerebral blood flow and an increase in mean arterial pressure.
Six days of chronic caffeine use resulted in the loss of the acute effects on mean arterial blood pressure, but not on blood flow. This indicates that there may be a development in peripheral tolerance but not central tolerance.
The headaches associated with caffeine withdrawal. This is experienced by some people and would be difficult to explain based on this research. The physiological effects of caffeine appear to last about 4 days.
Acute toxicity is characterized by…
- Vomit blood (Hematemesis)
- High resting heart rate (Tachycardia)
- Fast breathing (Hyperventilation)
- High blood sugar (Hyperglycemia)
- Ketones in urine (Ketonuria)
- Low potassium levels in the blood (Hypokalemia)
- Produce a lot of acids in the body (Metabolic acidosis)
Although deaths were linked with excessive caffeine intake. Cases of caffeine overdose are very rare! Because the subject will spontaneously and repeatedly vomit related to the intake of toxic caffeine levels.
The LD (the lethal dose for half the subjects) of caffeine has been estimated to be between 150 and 200 mg/kg.
A dose of caffeine that results in blood levels that exceed 100 µg/mL is considered lethal. Although acute toxicity begins at blood levels of 30 to 50 µg/mL.
A typical cup of coffee contains roughly 100 mg of caffeine and can increase blood caffeine levels to 1-2 µg/mL.
Several deaths have been connected with too much caffeine consumption. The most recent was a 22-year-old female who overdosed on diet pills.
A serum toxicology report indicated that her blood levels were in the range of 1500 µg/mL.
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