Topical Fat Loss: Capsaicin Cream Blunts Weight Gain in Rodent Model and Increases Leptin, Adiponectin, Lipolysis and Fatty Acid Oxidation in Visceral Fat Depots

Image 1: If you infused your ice-water with an extract of those, that could supercharge your "cold thermogensis" (see "Ephedra vs. Cold Thermogensis" ;-)

Those last 1-2lbs of stubborn fat have been and still are the focal point of countless of discussions among trainees, trainers and  magazines even average Joes and Janes who would not even remotely consider to go to the gym to get rid of those love handles - interestingly, all these groups are similarly susceptible to one message: "Revolutionary breakthrough in topical fat loss: "Whatever-Our-Marketing-Department-Came-Up-With-Burn will obliterate the stubborn body fat that's still covering your abs, obliges, butt, and whatever else you hate about yourself in record time!" Sounds and, as the countless disappointed testimonies on the Internet confirm, is usually too good to be true.

How many scoville (SHU) does it take to burn 1lbs of body fat?

A soon to be published study by researchers from the University of Ulsan in Korea does however show that many of the companies which advertise with the afore "cited" slogans could in fact be on the right track - at least with respect to one of the key ingredients many of those topical fat-burners contain: Capsaicin, a major pungent molecule that is found in hot chilies and other peppers and has already been shown to exert direct effects on isolated adipocytes in vitro (Kang. 2007; Hsu. 2007) and anti-obesity activity in animal models (Yoshioka. 1999; Zhang. 2007). Interestingly enough, epidemiological (Wahlqvist. 2001) and controlled human trials (Bloomer. 2010) suggest that these effect do - despite the often-touted differences in the thermogenic capacity of humans and rodents - in fact manifest in all the usual steps of scientific experimentation in the medical field, i.e. the petri dish, the animal model and the controlled, randomized, placebo-blinded human trial.

From the mouth onto the skin

As far as its topical usage is concerned the main focus of scientific research has yet been on the ameliorative effects of capsaicinoids on painful neuropathies and neuralgia (Harding. 2001; Roberts. 2011) and Lee et al. claim that their study is the first one to investigate the effects of in vivo application of 100mg of a 0.075% hydrophillic capsaicin cream applied to the shaved abdominal skin of pre-fattened mice who were pair-fed (=equal caloric intake for rodents in both groups to exclude reduced appetite as a cause for the observed effect) for 7-weeks.

Figure 1: Body composition (left) and adipocyte size (right) after 7-weeks on HFD with our without topical application of 100mg 0.075% capsaicin cream to the abdomen of obese mice (based on Lee. 2012)

As the data in figure 1 clearly shows, the topical application of capsaicin elicited similar beneficial effects on the blood lipids (not shown) as its oral ingestion in a previous HFD rodent trial (Kang. 2010). What is however particularly striking is that it did at the same time totally blunt further increases in body weight and reduced body fat storage in both the mesenteric, as well as the epididymal, visceral fat depots. The latter went hand in hand with profound changes in the adipocyte morphology of both fat depots which shifted from fewer large, to many small adipocytes - a feature which is usually associated with lower adipocyte inflammation and thus reduced risk of cardiovascular disease & co.

Topical application, systemic effects?

Both results, the improved lipid profile, as well as the reduction in visceral (intra- not super-abdominal) obesity appear to suggest that the effects of the capsaicin cream was by no means as localized as the producers of respective "supplements", would have it.

Figure 2: Adiponectin, leptin, TNF-alpha, lipoprotein lipase, UCP-2 and PPAR expression in mesenteric fat pads of the animals at the end of the 7-week study period (based on Lee. 2012)

The localized decreases in TNF-alpha, a central regulator or inflammation and the profound increases in adipokine expression (adiponectin + leptin), lipoprotein lipase, as well as UCP-2 and all three varieties of the peroxisome proliferator receptors (PPARs), Lee et al. observed in the mesenteric fat pads of the animals do yet confound this theory - capsaicin is, at least partially, a topical fat burner in the literal sense.

Caution! Stimulant-laden fire hazard!

Aside from the fact that its certainly non-negligible effects on visceral fat should not be of great interested for any avid trainee who is following a wholesome whole-foods diet, as those last slabs of body fat that are covering your abs belong to your subcutaneous and not visceral fat depots, there are two more things you should be aware of before you (most likely) waste your money on one of those products.

1. The capsaicin itself will make the body part you rub the product on look like a tomato on fire and burn worse than stinging nettle and that usually for hours!
2. The systemic effects of the stimulants most of these products contain can become an issue especially for leaner folks, as the dosages are usually adjusted for customers with a thick "insulation" that has to be penetrated, first. 

If you still feel that you have to give one or another of those preparations a shot, start with a moderate dose first and wait for a couple of hours to see what it does (don't expect it to do anything to your body fat in that time - if your waistline goes down within the first days of application that's simply water loss!).

My personal recommendation would still be to keep away from any of these products. Regardless of your personal tolerance to stimulants or the specific composition of the different formulas that are currently on the market - 99% of the feedback I have heard and read about states that these products are much better money- than fat-burners  ;-)

References:

1. Bloomer RJ, Canale RE, Shastri S, Suvarnapathki S. Effect of oral intake of capsaicinoid beadlets on catecholamine secretion and blood markers of lipolysis in healthy adults: a randomized, placebo controlled, double-blind, cross-over study. Lipids Health Dis. 2010 Jul 15;9:72.
2. Kang JH, Kim CS, Han IS, Kawada T, Yu R Capsaicin, a spicy component of hot peppers, modulates adipokine gene expression and protein release from obese-mouse adipose tissues and isolated adipocytes, and suppresses the inflammatory responses of adipose tissue macrophages.FEBS Lett. 2007;581:4389-96. 
3. Kang JH, Goto T, Han IS, Kawada T, Kim YM, Yu R. Dietary capsaicin reduces obesity-induced insulin resistance and hepatic steatosis in obese mice fed a high-fat diet. Obesity (Silver Spring). 2010 Apr;18(4):780-7.
4. Lee GR, Shin MK, Yoon DJ, Kim AR, Park NW, Yu R, Han IS. Topical application of capsaicin reduces visceral adipose fat by affecting adipokine levels in high-fat diet (HFD)-induced obese mice. Obesity (Silver Spring). 2012 Jun 18. doi: 10.1038/oby.2012.166. [Epub ahead of print]
5. Hsu CL, Yen GC Effects of capsaicin on induction of apoptosis and inhibition of adipogenesis in 3T3-L1 cells.J Agric Food Chem. 2007;55:1730-6. 
6. Wahlqvist ML, Wattanapenpaiboon N Hot foods--unexpected help with energy balance? Lancet. 2001;358:348-9.
7. Yoshioka M, St-Pierre S, Drapeau V, Dionne I, Doucet E, Suzuki M, Tremblay A Effects of red pepper on appetite and energy intake.Br J Nutr. 1999;82:115-23. 
8. Zhang LL, Yan Liu D, Ma LQ, Luo ZD, Cao TB, Zhong J, Yan ZC, Wang LJ, Zhao ZG, Zhu SJ, Schrader M, Thilo F, Zhu ZM, Tepel M Activation of transient receptor potential vanilloid type-1 channel prevents adipogenesis and obesity.Circ Res. 2007;100:1063-70.