2023 Worst Fat-Burning Supplements
By Robert Schinetsky
Fat loss is at the forefront of many individual’s minds this time of year. And with that comes an increased focus on improving the quality of one’s diet as well as his/her exercise habits.
It’s also natural for you to wonder about the utility or benefits of dietary supplements.
We’ve previously discussed the best-fat burning nutrients to consider when looking for an effective weight-loss support supplement. Today, we’re looking at the other end of the spectrum – those that you should avoid, or at the very least tread very carefully with.
So, without further ado, here’s the list of the worst fat-burning supplements of 2023.
Carnitine is as commonly seen in fat burners as caffeine is in pre-workouts. And, on the surface, it appears to make sense. Carnitine helps the body utilize fatty acids for energy, so by supplementing with more carnitine, you should be able to burn that much more fat.
Unfortunately, this is one instance where theory and real-life results don’t exactly match up.
For starters, regular L-Carnitine has terrible bioavailability, with research finding that L-carnitine supplements offer 5-18% bioavailability. This is in stark contrast to the bioavailability of dietary L-carnitine, which may be as high as 75%.1 It should also be mentioned that carnitine isn’t that hard to come by in the diet, especially for individuals who include animal-based proteins in the diet. Furthermore, carnitine deficiency is rare and it is NOT the rate-limiting factor in the body’s ability to utilize fat for fuel, which means supplementing with additional carnitine likely won’t yield tremendous benefits in terms of actual fat burning or weight loss.
In terms of recent research …
A published study in Clinical Nutrition found that daily consumption of 1,000mg L-carnitine had no beneficial effect on cardiometabolic outcomes or liver fat content in overweight or obese women with PCOS.2
An earlier study from November 2021 published in the European Journal of Nutrition examined a similar dosage of L-carnitine (1,000mg daily for 12 weeks) and found no benefit on lipid (fat) profiles).3
A 2020 meta-analysis of 37 randomized control trials assessing the effects of L-carnitine supplementation on weight loss and body composition noted:4
“It should be noted that L-carnitine supplementation resulted in 1.53 Kg and 1.29 Kg weight loss in participants with overweight and obesity, respectively. The reducing effect of L-carnitine on body weight was 1.08 kg in studies with follow-up period of 12 weeks and 1.48 kg in studies with follow-up period of >12 weeks. When considering these effects and also some mild side effects of L-carnitine including nausea, stomach discomfort (2 g/d)  and production of trimethylamine-N-oxide (TMAO is linked to an increased risk of atherosclerosis) [115,116], it seems that consuming healthy dietary patterns for weight loss is more logical compared with L-carnitine supplement. Because the same and even more weight reduction can be achieved by following healthy diets like Mediterranean , dietary approaches to stop hypertension (DASH) , vegetarian , low-fat , and low-carbohydrate diets [120,121] without considering the energy intake.”
Essentially, supplementation with carnitine may have a slight effect on weight loss in overweight/obese subjects over the course of 12 weeks, but it comes with the side effect of increased TMAO production, which is associated with an increased risk of atherosclerosis. Previous research also indicates that L-carnitine supplementation can increase the capacity of the gut microbiota to generate TMAO.5
Newly published research from the Cleveland Clinic led by Drs. Zhu, Hazen and colleagues (a research team that was instrumental in recognizing the link between elevated TMAO levels and the development of cardiovascular-related events) noted that dietary choline and TMAO (a metabolite of choline and carnitine breakdown) produced greater stroke size and severity.49 Additionally, May 2022 research published in the Journal of the American Medical Association (JAMA), in a study of 5,333 older adults enrolled in the Cardiovascular Heart Study, suggests that circulating TMAO is an important novel risk factor associated with risk of death among older adults.54 Individuals in the study with the highest levels of TMAO had a 20-30% higher risk of death. Also, higher blood levels of TMAO metabolites carnitine, choline and butyrobetaine was also associated with death among older adults. Betaine was not associated with risk of death.
The team of Zhu, Hazen and colleagues also found that transplanting gut microbes that contain an enzyme essential for choline-related TMAO production in the gut, called CutC, was enough to fuel increased stroke severity (over 2x larger!) and worsened outcomes (20-30% reduction in multiple functional outcome measures).49
This study demonstrated for the first time the impact that the gut microbiome can have on stroke severity and functional impairment following stroke.
The reason this study bears discussion is that carnitine (as well as choline) donors are found in countless dietary supplements, including fat burners, thermogenics and other weight-loss aids.
Harkening back to the findings from the 2020 meta-analysis, researchers also stipulate that equal or superior weight loss can occur through dietary manipulations4, such as the Mediterranean diet, which is known to be one of the best-viewed diets for cardiovascular health as opposed to relying on supplements, which may potentially increase the risk of cardiovascular-related events.
Now, you may be wondering, “what about vegans, vegetarians, and other populations that don’t consume enough animal proteins?” Could they benefit from carnitine supplementation?
A research paper from 2016 notes that:8
“Even though carnitine is present primarily in animal products, strict vegetarians (vegans) and lacto-ovo-vegetarians maintain normal carnitine levels, indicating that humans not only synthesize carnitine, but also effectively conserve it through renal tubular reabsorption.”
In other words, even individuals that don’t consume considerable amounts (or even adequate amounts) of dietary carnitine are able to maintain normal levels of carnitine, making the necessity or utility of L-carnitine supplements not necessary.
The takeaway here is that the beneficial application of L-carnitine supplements for weight loss is mixed at best. Some studies show minor benefits while others don’t. To top it off, researchers admit the dietary manipulations yield equal if not superior results. There’s also the carnitine-choline-TMAO connection to factor and the benefits/risks of using a supplement that may potentially increase your risk of cardiovascular-related events as well as the severity of them. Also, a recent six-month, double-blinded randomized placebo-controlled trial reported in the journal Nutrition & Metabolism progression of carotid artery atherosclerosis with L-carnitine supplementation.50-51 L-carnitine supplements also increased LDL and total cholesterol.
One of the newer supplements touted as a “powerful thermogenic” is GBB – gamma-butyrobetaine. It’s dubbed as a form a “super carnitine” capable of increasing carnitine excretion up to 300%.6,7
However, something to keep in mind is that just because the body may be excreting higher amounts of carnitine doesn’t mean it’s necessarily deriving benefit from it.
But, before we get to that, let’s explain a bit more about why GBB is included in weight-loss supplements.
GBB was discovered because of its role as the proximate endogenous intermediate in carnitine production. It is converted to carnitine via the actions of an enzyme called gamma-butyrobetaine dioxygenase. This takes place during a multistep biological process that synthesizes carnitine from lysine – an essential amino acid.
Similar to carnitine supplementation, the thinking with GBB is that supplementing with it will force the body to generate more carnitine, which will lead to greater fat oxidation (and hopefully weight loss).
Some of the earliest research into GBB found that even after 10 days of supplementation at levels ranging between 37.5-75mg/kg per day (which, by the way, are orders of magnitude higher than what are found in dietary supplements…which are commonly dosed at 25-50mg TOTAL) DOES NOT influence muscle carnitine levels.6
What this means is that GBB isn’t enhancing your muscle’s ability to utilize fat for energy (i.e., fat burning).
Yes, GBB supplements may produce profound sweating and an overheated sensation, but in terms of actual hard data showing it enhances fat burning or weight loss, there is none as of this publication.
In other words, there’s no credible evidence to date showing that GBB is an effective supplement for weight loss.
Another very common (yet equally suspect) fat loss supplement in conjugated linoleic acid (CLA).
It is a type of polyunsaturated fat that’s naturally occurring in beef and dairy and can be found throughout the body.
Some research has given evidence that CLA may indeed help individuals lose body fat.9,10
However, the “big picture” is conflicted at best as there are just as many studies (if not more) demonstrating that CLA supplementation is NOT more effective than placebo, and in some instances, CLA supplements actually result in weight gain!11,12
But, weight gain isn’t even the worst potential drawback of CLA supplements.
Two different meta analyses from 2017 stated CLA supplements increased certain inflammatory markers, including c-reactive protein (CRP) and tumor necrosis factor-α (TNF-α).13,14
This is particularly disturbing when you consider the fact that chronic, systemic inflammation is an key factor in a wide array of diseases including:
Irritable Bowel Syndrome
Chronic Obstructive Pulmonary Disorder (COPD)
Additional research also suggests that consuming large doses of CLA supplements can lead to fat buildup in the liver, which is an indicator of diabetes and metabolic syndrome.15,16
CLA also has been documented to lead to other less severe side effects including:
Flatulence (something we all want from our weight-loss supplement)17
To top it off, CLA supplements may also lead to insulin resistance and reduce levels of HDL (“good”) cholesterol.18,19
The list of new “designer” stimulants that enter the supplement industry is a revolving door of questionable ingredients that could be described as “gray area” at best.
This includes the likes of:
DMBA (AKA AMP Citrate)
DMHA (AKA Juglans Regia Extract, 2-amino-6-isoheptane, 2-amino-5, etc.)
Some less “aggressive” yet equally unproven stimulants you’ll see used in various fat burners and appetite suppressants include:
Without going into a lengthy explanation of each and every stimulant, understand that each and every one of these has a severe lack of research behind it demonstrating its effectiveness for weight loss or its safety.
Side effects for the aforementioned stimulants include elevated heart rate, increased blood pressure and vasoconstriction. Again, these stimulants are thoroughly lacking in human studies and have virtually no evidence supporting their utility or safety for fat loss.
This is why AML™ THERMO HEAT® and AML™ THERMO HEAT® COCKTAIL™ only utilize caffeine and citrus aurantium (which supplies p-synephrine). These two stimulants have been studied numerous times in healthy human subjects and found to not only be effective but (more importantly) safe.20,21,22
GREEN TEA EXTRACT
This one may come as a surprise to many of you considering the ubiquity with which green tea extract is found in dietary supplements.
And, truth be told, there is some evidence indicating that green tea extract may support weight loss.23,24
However, there are also a fair number of studies demonstrating no benefit from green tea extract.25,26
Some researchers contend that the conflicted results of green tea extract may be due to the administration method, and that for optimal absorption, individuals need to consume green tea extracts on an empty stomach as co-ingestion with food, especially protein, reduces absorption of tea catechins.
Nevertheless, a 2014 systematic review and meta-analysis of the available literature at the time concluded:
“Green tea or green tea extracts intake or its extracts exerts no statistically significant effect on the weight of overweight or obese adults. There is a small effect on the decrease in the percentage of fat mass, but it is not clinically relevant.”28
Furthermore, a recent meta-analysis found that green tea extracts were ineffective at improving glycemic control in diabetics.30
There’s also the often overlooked hepatotoxicity risks of green tea extract intake:
In 2017, Health Canada reviewed the potential risk of hepatotoxicity associated with green tea extract and strengthened the cautionary risk statement in their green tea extract monographs.31
The 2018 EFSA (European Food Safety Authority) review of catechins in green tea concluded that clinical studies indicate that intake of green tea extract supplying EGCG amounts equal or above 800 mg daily increased serum transaminases, which is indicative of liver injury. The review further concluded that it was not possible to identify an EGCG dose from green tea extracts that could be considered safe because in one case, intake of 375 mg of an 80% ethanolic extract resulted in hepatotoxicity.32
The 2020 U.S Pharmacopeia (USP) comprehensive review on green tea extracts noted: “Our review shows a clear occurrence of severe hepatotoxicity from ingestion of GTE in humans albeit with very low frequency and further suggests that specific GT constituents, particularly EGCG and other catechins found in GTE, are likely to be involved in the observed hepatotoxicity.”33
At the end of the day, you have to decide for yourself whether a minor (non-statistically significant) loss of body weight is worth jeopardizing the health and function of your liver. From the research side of things, it is not worth the potential risk.52
A safer alternative would be to consume actual green tea instead of concentrated extracts, as the consumption of green tea is linked to numerous health benefits (including supporting liver health) as well as enhanced brown fat thermogenesis.29
Hoodia is a cactus-like plant found in the Kalahari Desert in Africa.
Traditionally, the plant was consumed when food and water were in short supply to help stave off hunger and thirst.
Hoodia became a popular inclusion in dietary supplements when it appeared that some of the bioactives in the plant (such as P57) cause increased ATP production in the hypothalamus and/or it could act on the bitter taste receptors resulting in the secretion of CCK – leading to appetite suppression.
However, there is a succinct lack of quality human evidence demonstrating either of these activities.
Moreover, not only does research find hoodia ineffective for weight loss, it indicates it could be dangerous.34,35,36
EPHEDRA NEVADENSIS/EPHEDRA VIRIDIS
Ephedra was one of the most popular, well-studied, and effective stimulants for fat loss due to it reducing appetite and increasing energy expenditure. It was particularly helpful for reducing “stubborn” fat by increasing the activity of beta-receptors, which stimulates the release of energy stored in the fat cell.
Research shows that ephedrine significantly increases fat burning, and it also works synergistically with caffeine, which we know can have an effect on weight loss.37,38,39
This led to the creation of the very popular “EC” stack, and it was found in research to boost metabolic rate ~5%, which yields about an additional ½ pound of fat loss per week.40
Steve Blechman used the powerful combination of 200mg caffeine + 20mg ephedra in TwinLabs Ripped Fuel when ephedrine was legal for use in dietary supplements.
However, ephedrine is no longer allowed in dietary supplements, yet some companies still include ephedra extracts in their weight-loss supplements. These extracts (derived from ephedra nevadensis and ephedra viridis) do NOT contain ephedrine alkaloids, which relegates it basically to a form of tea extract, which may or may not work.
More than likely, supplement companies are including on the label to trick consumers into thinking the product contains ephedrine (which it won’t).
EXOGENOUS KETONES (BHB SALTS)
Ketogenic and low-carb diets have been popular for several years now, and (like many other diets) can be effective for reducing body weight and body fat levels.
Concomitant with the surge in popularity of keto diets can be a dramatic increase in the number of functional foods and dietary supplements claiming to be “keto friendly” or help you get into ketosis.
The most well-known of these in the realm of dietary supplements were exogenous ketones, such as BHB salts and ketone esters.
Exogenous ketones are advertised to help:
“ease” the transition into ketosis
reduce symptoms of “keto flu”
“teach” the body how to burn fat for fuel (among other things)
Essentially, exogenous ketones provide the body with a readily accessible fuel source, while your body burns through its glycogen stores, thereby accelerating the transition to running on ketone bodies and entering nutritional ketosis.
However, there is a considerable lack of research regarding exogenous ketone salts and ketone esters demonstrating that supplementation eases the transition to ketosis or reduces symptoms of “keto flu” (i.e., brain fog, lethargy, muscle cramps, headaches, constipation).41
As for helping burn body fat, BHB salts aren’t much better either as instead of actually burning body fat, when you consume exogenous ketones, your body’s downregulates its own (endogenous) production of ketones, thereby limiting your body’s ability to run on stored fat. After it finishes burning the exogenous ketones for energy, it will resume ketone generation from body fat stores.
Furthermore, the body has assorted feedback mechanisms that reduce ketone production if ketone levels rise too high. In other words, if you’re chugging exogenous ketones all day long, your body will reduces its own ketone production to prevent your blood from getting too acidic.42,43,44 A superior option would be MCT oil, which can be readily used by muscle cells for energy as well as stimulate the body to naturally produce its own ketones. This is why AML™ THERMO HEAT® PROTEIN includes MCT Oil Powder instead of BHB Salts.
There’s more, though.
Ketone supplements don’t really seem to offer much benefit in terms of exercise performance either. They have been noted to increase blood levels of BHB in the body, but in terms of actually improving performance, reducing fatigue, improving recovery, or benefiting metabolic shifts in fuel utilization (i.e., helping the body burn more fat for fuel), the research isn’t very complimentary.45,46,47,48,53
Taking all of this into account, it’s hard to justify purchasing a supplement that is equally costly, ineffective and terrible tasting. The current body of evidence does not support the use of exogenous ketones for fat loss or improving exercise performance.
At the end of the day, diet and exercise remain the foundation for weight loss and body composition. No supplement can replace proper eating and hard training.
When those factors are in place, though, there are a select group of supplements that can benefit those seeking weight loss (not the ones listed above, obviously).
At Advanced Molecular Labs (AML™) we decided not to incorporate any of the above ingredients due to the lack of scientific data to support their use.
© Copyright 2022 Advanced Research Media
© Reprinted with permission from Advanced Research Media, Inc.
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