Sesamin is a lignan abundant in sesame seeds. Studies have found Sesamin to help reduce cholesterol, help fat metabolism, and improve health. Sesamin is used as an active ingredient in various fat burners and diet pills such as Lipoderm, Slimquick, and you can also find pure sesamin supplements such as Scivation Sesamin. But does it really help burn fat? We did some digging and will discuss in some detail below.
There are many clinical studies done on the various effects of sesamin - most using rats, and very limited few using human subjects. However when it comes to the fat metabolism and weight loss effects of sesamin, I'm unable to find any studies done using human subjects. Various studies have found sesamin to be anti-hypertensive (reduce high blood pressure), helps to increase nitric oxide, increases fatty acid oxidation, lowers serum lipid levels, and it also has anti-oxidant properties and can be classified as a pro-antioxidant.
When sesame lignans are fed to rats, it is found that sesamin protects against induced oxidative stress.  Sesamin can also be classified as a pro-antioxidant. Sesamin is metabolized in the liver to mono- or di-catechol metabolite - both of which exhibits antioxidant activities. 
Studies have found sesamin to be anti-hypertensive. A Taiwanese study found that sesamin increased the nitric oxide (NO) concentrations, and that sesamin may help improve hypertension because of its ability to induce NO. 
Does Sesamin Oil Burn Fat?
While being an antioxidant and having anti-hypertensive properties makes sesamin seem like a promising supplement; however, this is not what has caught the attention of most people. It is the findings that sesamin can help increase fatty acid oxidation, and have fat burning applications that has put sesamin into the spotlight.
Sesamin is one of the most abundant lignans in sesame seeds. Various studies have shown that sesamin helps reduce fat and improve health. Below are 2 illustrative studies done on Sesamin:
Sesamin, a sesame lignan, is a potent inducer of hepatic fatty acid oxidation in the rat. Ashakumary L, Rouyer I, Takahashi Y, Ide T, Fukuda N, Aoyama T, Hashimoto T, Mizugaki M, Sugano M.
Laboratory of Nutrition Biochemistry, National Food Research Institute, Ministry of Agriculture, Forestry and Fisheries, Tsukuba, Japan.
The study examined the effects of sesamin on hepatic fatty acid oxidation in rats that were fed various amounts of sesamin for 15 days - separated into 4 groups fed with 0%, 0.1%, 0.2%, 0.3%, and 0.4%. Mitochondrial activity almost doubled in rats on the 0.5% sesamin diet. Peroxisomal activity increased more than 10-fold in rats fed a 0.5% sesamin diet in relation to rats on the sesamin-free diet. They found that dietary sesamin greatly increased the hepatic activity of fatty acid oxidation enzymes, leading to the conclusion that "an alteration in hepatic fatty acid metabolism may therefore account for the serum lipid-lowering effect of sesamin in the rat".
Metabolism. 1999 Oct;48(10):1303-13.
Sesamin, a sesame lignan, as a potent serum lipid-lowering food component. Personal Authors: Ide, T., Kushiro, M., Takahashi, Y., Shinohara, K., Fukuda, N., Sirato-Yasumoto, S.
Author Affiliation: Division of Food Functionality, National Food Research Institute, Tsukuba, Ibaraki 305-8642, Japan.
This research examined the effect of sesamin on the hepatic fatty acid metabolism in the rat. The rats were fed different levels of sesamin, and the researchers found that rats fed the highest levels of 0.5% sesamin in their diet had double the mitochondrial activity, and 10 times high perioxisomal activity. The study concluded that sesamin affects the fatty acid metabolism and lipoprotein production in the liver, and hence lowers the serum lipid levels
Document Title: JARQ, Japan Agricultural Research Quarterly, 2003 (Vol. 37) (No. 3) 151-158
Another Japanese study fed rats with either a low fat diet or a high fat diet with or without sesamin for a four week period. After the four weeks, it was found that total fatty acids in the liver increased significantly from the high fat diet; however, the high fat diet rat group that was also fed sesamin had almost the same fatty acid concentrations as the low fat diet group. Theses results suggest that sesamin suppressed the increase of fatty acid concentration caused by the high fat diet. 
From these studies (among many others), sesamin sounds like a promising supplement for losing fat and losing weight. However, keep in mind that all these studies were performed using rats. I was unable to find any weight loss studies of sesamin performed using human subjects - so, how effective sesamin is for humans still need further research and studies.
Scivation Sesamin Supplement
A popular sesamin product is Scivation Sesamin, which contains a high grade extract of sesamin. Each capsule contains 1,000mg (1g) of sesame oil, and is standardized to 500mg of sesamin. To buy scivation sesamin oil, please follow the links below:
2. Biofactors. 2004;21(1-4):191-6.
Antioxidative roles of sesamin, a functional lignan in sesame seed, and it's effect on lipid- and alcohol-metabolism in the liver: a DNA microarray study. Kiso Y.
3. J Hypertens. 2004 Dec;22(12):2329-38.
Sesamin induces nitric oxide and decreases endothelin-1 production in HUVECs: possible implications for its antihypertensive effect.
Lee CC, Chen PR, Lin S, Tsai SC, Wang BW, Chen WW, Tsai CE, Shyu KG.
4. J Nutr Sci Vitaminol (Tokyo). 2003 Oct;49(5):320-6.
Effect of dietary fat level and sesamin on the polyunsaturated fatty acid metabolism in rats.
Mizukuchi A, Umeda-Sawada R, Igarashi O.