In the first part we  explain the fundamental aspects of the process of fat loss , and the basic physiology of our most hated cell, the adipocyte .

This knowledge will help you better understand the mechanisms of operation of the main supplements , which is precisely the subject of today.

We analyzed ten of the most popular fat-burning supplements : caffeine, synephrine, green tea / EGCG, forskolin, garcinia cambogia, yohimbine, green coffee extract, L-carnitine, medium chain triglycerides and conjugated linoleic acid.

You will learn which ones have scientific support and which ones do not, the recommended doses and possible risks of each one.


Caffeine is one of the most effective supplements when it comes to improving athletic performance , and also helps in the fat burning, acting in two main ways:

It elevates adrenaline , increasing the activation of β- adrenergic receptors   and therefore the production of cAMP.

Inhibits the action of phosphodiesterases , enzymes that degrade cAMP. This maintains high levels of cAMP, activating HSL, the main fat-burning lipase, to a greater extent.


Synephrine is the main active compound of bitter orange peel , classic in traditional Chinese medicine.

It is a beta-agonist, increasing the activation of β- adrenergic  receptors  and thus elevating fat burning ( study ). As a result, a dose of 50 mg raises the metabolism by about 65 calories, without affecting blood pressure ( study ).

The mechanism of action is similar to ephedrine , but with a  more selective action . While ephedrine stimulates several alpha and beta receptors, which control the cardiorespiratory system, synephrine stimulates only the beta receptors responsible for the mobilization of fat ( detail ), thus avoiding the typical risks of ephedrine (tachycardia, hypertension, etc.). . It is therefore considered much safer ( detail ).

Acts synergistically with caffeine, both in terms of physical performance and fat loss ( study ).


In addition to providing caffeine (although to a lesser extent than coffee), green tea contains several  catechins with multiple properties, helping to control weight by different mechanisms ( detail ).

The  EGCG (epigallocatechin gallate or) is the most active catechin, and offers synergies with caffeine ( meta – analysis ). While caffeine elevates catecholamines, EGCG inhibits an enzyme that degrades them , prolonging its effect.

The results of studies with green tea are inconsistent, probably because they provide insufficient amounts of EGCG in its natural form (one cup is about 100 mg) ( detail ). This study, for example, concludes that 300 mg / day does not cause weight loss. The effect is especially poor in sedentary people ( study ), working better when combined with exercise ( study ).

Studies with higher doses do show favorable results ( study , study ), and the effective dose is estimated at 400-500 mg / day for the majority ( study ). If you buy green tea extract, keep in mind that 50% is EGCG. To achieve these amounts with green tea you should take four or five a day.

To maximize the absorption of EGCG should be taken in fasting ( study ), ideally before exercise. As I explained in this podcast ,  matcha has become my favorite green tea, and taken before exercise elevates fat oxidation ( study ).

The absorption of EGCG is greater in fasting

Although at the time of losing fat the extracts are more effective, do not forget that green tea is much more than its catechins , and its contribution of L-theanine is also remarkable . This amino acid relaxes the nervous system ( study , study ), counteracting the effects of caffeine but without interfering with care  ( study ).


It is a compound obtained from the Coleus Forskohlii plant , classic in this case of Ayurvedic medicine.

Coleus Forskohlii

Forskolin increases the intracellular levels of cAMP in adipocytes ( study , detail ), facilitating the activation of HSL .

A study in overweight people concluded that forskolin supplementation reduced the percentage of fat, in addition to raising testosterone. In vitro studies seem to confirm this increase in testosterone, but the evidence is still scarce.

A later study in women did not confirm the fat-burning effects, but it did mitigate the weight gain . Another  more recent study shows that it elevates lipolysis and prevents fat gain, but it was in rats.

In summary, it is a promising supplement but the evidence is reduced as fat-burning , although it seems to provide additional benefits such as reducing blood pressure ( study ).

Dosage: 50 mg / day (or 500 mg of a 10% extract), ideally divided into two doses.

We could summarize the effect of these four substances with the following diagram.

Effects and synergies between caffeine, EGCG, synephrine and Forskolin


Garcinia Cambogia is a small pumpkin-shaped fruit, native to Asia. Its main active compound is  hydroxycitric acid (AHC) , an inhibitor of the enzyme ATP-citrate lyase.

By inhibiting this enzyme, it is difficult to produce fatty acids from carbohydrate , favoring the accumulation of glycogen ( detail ). This could reduce appetite and limit caloric intake, facilitating weight loss ( study ,  detail ).

In athletes can reduce glycogen consumption, by increasing fat oxidation ( study , study ).

A systematic review of nine studies on Garcinia Cambogia concludes that a positive but small effect on weight loss is observed .

Some studies in rats warn of possible toxicity at high doses ( study , report ), and given that the weight losses registered are limited (1-2 Kg on average) it surely does not compensate the money .


Yohimbine is extracted from the bark of an African tree, and was originally used as a treatment for erectile dysfunction ( detail ).

In the first part we saw that beta receptors facilitate lipolysis, but adipocytes also have alpha receptors (specifically alpha-2), whose activation produces the opposite effect:  interfering with the action of catecholamines ( study ,  detail , detail , detail ).

Yohimbine blocks these alpha receptors , potentiating the action of catecholamines and elevating fat burning. These receptors are especially numerous in the fat of the  abdominal area in the case of men and in the gluteofemoral fat  in the case of women , being an especially effective supplement against the famous rebel fat .

A study in women with obesity, during three weeks, showed greater loss of fat in the group that was taking yohimbine compared to those that used a placebo. And the same thing confirms this other study in soccer players, also of three weeks.

It is also true that some  studies  show no effect, perhaps by the time the supplement is taken. Insulin inhibits the effect of yohimbine , while exercise amplifies it ( study ). Therefore, the optimal moment for its taking would be before performing a fasting training ( study ), lengthening the post-training fasting by two hours. The increase in fat burning also seems to improve physical performance ( study ).

A dose of   0.2 mg / kg seems safe and effective in most. For possible side effects, it would be advisable to start with half (0.1 mg / kg) to assess individual tolerance.

In people with sensitivity, yohimbine can cause   tachycardia, arrhythmias, anxiety, impulsivity and an increase in blood pressure ( study , study ,  study , study ). It should not be used in people prone to panic attacks ( detail ).

It is a supplement whose dosage should be well controlled, and given the important variations between the concentrations reported on the labels and the actual ( study ), yohimbine is currently banned in many countries, although it is not difficult to find.


Coffee is much more than caffeine, and contains for example  chlorogenic acid , which in addition to its antioxidant properties seems to help reduce blood glucose ( study , study ).

When roasting coffee, however, much of this compound is destroyed, hence the interest of green coffee supplements, before being roasted.

Life of coffee. Marked with an arrow the moment where green coffee is considered (before being roasted)

Although there are some studies that demonstrate its effectiveness when losing fat ( meta-analysis ), the results are actually equivalent to normal coffee , indicating that caffeine is probably the main factor.

Since the evidence is scarce and that the green coffee extract is more expensive than normal, it is not a supplement that recommends buying .


The fat is finally oxidized in the mitochondria , and carnitine helps the fatty acids cross the mitochondrial membrane ( detail ).

Carnitine facilitates the entry of fatty acids into the mitochondria to be oxidized (for example in the muscles)

Despite being a popular supplement, it has low effectiveness . To begin with, the body synthesizes the carnitine it needs , and  meat is also a good additional source. Carnitine deficiencies are therefore rare, and supplementation does not elevate muscle carnitine ( study ). Except isolated cases, it does not contribute anything in terms of fat burning ( study ).

If we talk about performance, the results are not encouraging either. Most studies show no benefit (as this recent study ) although in others it is observed that carnitine could help to conserve glycogen ( study , study , study ) and accelerate muscle recovery ( study , study ), but not very significantly and without elevating fat burning.

That does not mean that it is a supplement without any basis, and there are studies that show benefits in other aspects, but burning fat is not one of them.


Medium chain triglycerides are a special type of fat that is processed quickly. They pass directly from the intestine to the liver, without the need to cross the lymphatic system like other fatty acids.

In addition, they can cross the mitochondrial membrane without the help of transporters , whereas long-chain fatty acids require carnitine, slowing down the process ( detail ,  detail ).

In conditions of low hepatic glycogen, medium chain triglycerides easily raise the production of ketone bodies , suppressing the appetite , increasing energy expenditure ( study ) and thus facilitating fat loss ( meta-analysis ).

I am not in favor of bulletproof coffee ( here I explain why ), but having a coffee with a spoonful of medium chain triglycerides can help you start the day with energy, lengthening the nighttime fast and reducing the total caloric intake ( more detail ).

Do not expect surprising results but they can help, and by stimulating the production of ketone bodies they are an interesting supplement in the context of a ketogenic diet .

Important notes:

The coconut oil has its own benefits, but less than half of the fatty acids are medium chain produce less satiety ( study ). For that reason, if we talk about supplements, it is more advisable to use pure TCM,  like this one .

As explained in De Cero to Ceto , producing more ketone bodies is not synonymous with burning more fat , and the ultimate goal is to produce these ketone bodies from our own stores of fat, not supplements. That said, the satiating effect can compensate and help boost the total caloric deficit.

If you decide to try, start with small doses (no more than one or two tablespoons daily). Some people notice intestinal problems with higher doses.


The trans fats have a bad reputation, largely deserved part. When the unjust war against saturated fat began , it was replaced by trans fats obtained by hydrogenating vegetable oils ( detail ). The margarine dethroned the butter , and the result was tens of thousands of unnecessary deaths ( detail ).

However, not all trans fats are the same , and conjugated linoleic acid (ALC) is a good example. Chemically it is a trans fat present in small quantities in meats and  milk fat , especially in the case of  grass-fed cows .

This fat present in food is beneficial, and people with more ALC in their body have less risk of coronary heart disease ( study ) or diabetes ( study ). However, it is not clear that we can achieve these same effects with supplements.

There are 28 different forms of ALC ( detail ), although the most studied are cis-9, trans-11, trans-10 and cis-12. These variants (or isomers) appear in different ratios in food than in supplements.

Different combinations produce different effects ( study ) and in some cases adverse results have been seen , linked for example to increased inflammation and oxidative stress .

The different isomers (molecules with the same formula but different structure) of ALC vary in the position of their double bonds

Perhaps for this reason the evidence is so heterogeneous . Some studies indicate that they can help with the loss of body fat in doses of 3-6 g / day ( study , study , study , study ), but  many others conclude that they do not ( study ,  study , meta-analysis , study ).

This inconsistency is reflected in the conclusions of this  meta-analysis  and this review , which do not find clear evidence of its benefits .


As we saw in the first part, the supplements are only a small piece of your strategy . The pillars will always be food , training and rest . If these large pieces are in place, supplements can help.

In fact, we saw that certain supplements are only effective if we add them to exercise . Some help, for example, to increase lipolysis, but if the released fatty acids are not used, they will simply end up accumulating elsewhere.

Effectiveness : according to the magnitude of the results demonstrated, its consistency and the amount of evidence.

Risk : evaluated based on the reported adverse results and the number of studies performed (the fewer studies the less certainty exists about their safety). Although all the above substances are considered safe, some present more risks than others ( detail ). In any case, it is advisable to always start with the lower range of effective doses .

Accessibility : considering both the price and the ease of access to each supplement.

Based on the above criteria, I propose a final recommendation for each supplement, where more ” checks ” imply better total valuation.


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