Supplements to Boost Your Fat Oxidation (#48)

Finding a supplement that enhances the body's ability to burn fat during activity sounds like a convenient shortcut. The question is, how effective are they in practice? In this article, we explore what research says about supplements that can impact fat oxidation during endurance training. The basic premise is straightforward: the body's carbohydrate stores are limited, while fat reserves are considerably larger. If the body can utilize more fat at a certain intensity, glycogen is conserved, potentially improving endurance. Through a review of research, we dive into which supplements are actually supported by studies—and which ones you might as well disregard.

Question 1 – why bother with this? While it's true that fat requires more oxygen to burn than carbohydrates and can increase the risk of gut issues, both of these statements hold. However, since our muscle glycogen and our ability to absorb and burn carbohydrates are limited, fat oxidation remains crucial—especially when you're active for more than an hour.

At rest, fat is the body's primary fuel source. During physical activity, glycogen takes precedence, though protein still contributes to some extent. If alcohol is in the mix, it takes priority, but that's a topic for another time 🙂

The aim is to elevate the usage of fat as an energy source as the intensity goes up, enhancing the body's capacity to derive energy from fat. For more details, check out our articles on Train Low – Compete High, part 1 and part 2 here. In short, these methods help train mitochondrial numbers, lipase activity (the enzyme responsible for breaking down fat), and other factors that limit fat oxidation.

Let's shift our focus to the supplements that can aid in boosting fat burning during physical activity.

We've reviewed an article titled "Nutrition Supplements to Stimulate Lipolysis: A Review in Relation to Endurance Exercise Capacity" published earlier this year. So, let's explore the supplements.

The supplements that have been explored in this area and have in some way impacted fat oxidation, thus qualifying for this review, are:

• Caffeine
• Green Tea Extract
• L-Carnitine
• Garcinia Cambogia (hydroxycitric acid)
• Capsaicin
• Ginseng
• Taurine
• Silk Peptides
• Octacosanol

The review examined both animal and human studies. Several supplements showed positive effects in animal studies but did not translate to humans. The supplements that have demonstrated effects for us athletes are listed below.

To determine if something requires more or less oxygen, an oxygen uptake test is necessary. Typically, the test participant wears a mask in a semi-closed or closed system, and researchers measure the inhaled and exhaled air to assess the levels of oxygen and carbon dioxide. This allows for the calculation of the proportion of energy derived from fats versus carbohydrates using the respiratory quotient (RQ). A lower RQ indicates a greater proportion of fat burning.

In intervention studies, two identical tests are often conducted: one following the intake of the active substance and the other after a placebo. The tests are performed at the same load (often 60–70% of VO2max) so that the only variable is the supplementation. If RQ decreases with the supplement’s intake, it shows that more fat is being utilized at that specific intensity, essentially conserving muscle and liver glycogen.

It is important to note that the results are generally relevant to the tested intensity. Some substances may influence fat oxidation even at higher intensities, but such a conclusion requires specific testing.

Caffeine is the most effective enhancer of fat oxidation. Numerous studies show performance improvements following caffeine consumption, and when measuring RQ, there's a consistent increase in fat oxidation.

As early as 1978, a study indicated that a small group of cyclists could cycle for 90 minutes instead of 75 at a given load after consuming 330 mg of caffeine. This was at up to 80% of VO2max (88% of max pulse) — those who had caffeine burned 1.31 g/min of fat compared to 0.75 g/min in the control group.

The majority of studies report similar effects at doses ranging from about 2–13 mg/kg of body weight. Many of the performance gains in longer distances can be attributed to caffeine's ability to enhance fat oxidation at a given heart rate, thereby conserving glycogen. For more on caffeine and dosages, check out our previous pod/article on caffeine.

Green tea (Camellia sinensis) has been extensively studied. About 35% of the leaf is made up of polyphenols, of which 70–80% are catechins. These substances activate hormones and enzymes that facilitate the breakdown of stored fat, making it available as fuel.

The evidence for green tea is not as strong as for caffeine, but it is present. Jeukendrup et al. conducted a study in 2008 where participants received capsules with 890 mg of polyphenols or a placebo during the last 24 hours before the test. The groups that received polyphenols saw an increase in fat oxidation from 0.35 g/min to 0.41 g/min. The conclusion is that green tea can likely increase fat oxidation at moderate intensity (about 60% VO2max) when consumed in the range of 200–800 mg/day over several weeks (5–8 weeks).

L-Carnitine acts as a messenger, transporting fatty acids into the mitochondria where energy is produced. Since transport into the mitochondria can be a potentially limiting step, supplements have been studied to determine their effectiveness.

Research since the 1980s has shown mixed results. The body typically synthesizes the necessary amount of L-Carnitine, making supplements generally unnecessary. However, there is evidence suggesting positive effects for athletes with high training volumes where the body's production might not suffice.

The review concludes that 2-4 g/day can be beneficial during periods of high training volume. The goal is to help the body utilize more fat as fuel during numerous sessions, conserve glycogen, and thereby reduce overall strain on the body. However, if any effects occur, they are minimal.

Garcinia Cambogia (hydroxycitric acid), capsaicin, ginseng, taurine, silk peptides, and octacosanol have shown either no effect or only a very weak increase in fat oxidation in athletes. Some have reported positive findings in animal studies, but the evidence in humans is weak or nonexistent. In short, you can essentially eliminate them from your list if your goal is to enhance fat oxidation through endurance training.