Numerous weight loss articles and forum posts tout the virtues of cinnamon, commonly saying that it increases metabolism twenty fold and is therefore a useful supplement for weight loss. Sorry folks, but this is wrong on too many counts to count! That said, the research does show that cinnamon has beneficial effects on blood pressure and body composition, so that's good news, but not dramatic.
First off, let's just put on our BS detectors. If cinnamon did increase metabolism 20 fold, we should be able to eat a little cinnamon and lose weight like mad all day long. If you burn 2,000 calories, with a little cinnamon, you'd now be burning 20,000. If you were holding even at 2,000 calories, you would now be losing five pounds per day: (20,000 kcal - 2,000 kcal) / 3500 kcal/pound of fat = 5.14 pounds of fat. Obviously, this can't be so. Since I love to put cinnamon on my oatmeal, at that rate, I would be entirely wasted away to zero pounds after less than a month.
What Does the Research Say about Cinnamon?
Richard Anderson, a scientist with the USDA Agricultural Research Center studied numerous compounds found in cinnamon to see what their effect was on sugar metabolism, publishing their results back in 2000. Anderson's team did find that one compound in cinnamon, methylhydroxy chalcone polymer (MCHP), increased metabolism of sugar by fat cells twenty fold. Now a few things about this.
- These experiments were done in vitro, that is in the test tube, and it is not clear how they apply to humans.
- MCHP is only one compound in cinnamon. That's analogous to, for example, vitamin C in an orange. Fresh, tree-ripened oranges are rich in vitamin C, but they only contain 45mg per 100g (so about .001% by weight). I don't know the proportion of MCHP in cinnamon (and scientific studies differentiate between common and cassia cinnamon, which can have different amounts of various compounds), but cinnamon could be an "excellent" source of MCHP while at the same time having only trace amounts.
- Most importantly, what this studied measured was the ability to move sugar from the blood stream into a fat cell. Normally, insulin opens the gateway that lets our cells take up sugar. The finding here was that MCHP essentially enhanced the effect of insulin. Remember, the role of insulin is as follows: "In adipose tissue, glucose is converted to fatty acids for storage as triglyceride" . In other words, it helps you make fat (it also helps get glucose and amino acids into muscles — insulin is a good thing, but it's important to understand it's role. In people suffering from type-II diabetes, insulin has a hard time opening those gateways, and they have difficulty metabolising sugar. In this context, that means they have trouble getting sugar out of their bloodstream and into their cells. MCHP was shown to improve that process dramatically in the test tube. However, this does not mean that the fat cells burned more calories. It means they were better at absorbing sugar and making fat out of it. So while that might be good news for diabetics in that it might cut down on the amount of insulin they need to take and might make it easier to regulate blood sugar, it really doesn't mean anything at all for non-diabetic dieters who are producing normal amounts of insulin. In fact, it means that your fat cells are more efficient at absorbing calories from your blood stream. That's a good thing for your health — provided you're taking in the right amount of sugar and the right number of calories, but it is not going to help you lose weight.
With all that said, 2000 is getting to be a long time ago and so, of course, there have been followup studies and reviews of followup studies. The most comprehensive review of placebo-controlled human studies found that
These data suggest that cinnamon has a possible modest effect in lowering plasma glucose levels in patients with poorly controlled type 2 diabetes .
Another review study found that
Two of 3 randomized clinical trials on type 2 diabetes provided strong scientific evidence that cassia cinnamon demonstrates a therapeutic effect in reducing fasting blood glucose by 10.3%-29%; the third clinical trial did not observe this effect.
None of these studies suggest health benefits that encourage weight loss or are of particular help to people without type-II diabetes.
Some Good News for Dieters
At the outset, I promised some good news, so here it is. Anderson has done more recent experiments on human subjects  and found that, in addition to the antioxidant properties of the polyphenols in cinnamon, an extract of water-soluble compounds in cinnamon was found to increase lean body mass by 1.1% and decrease body fat by 0.7% compared to the placebo group, measured over twelve weeks. This effect had a high confidence interval, so it is not likely to be random, but the effect is, as you can see, quite mild compared to the claims of a 20-fold increase in metabolism. One more note: the reason they conducted these tests with Cinnulin, an extract of water-soluble compounds, is because the fat-soluble compounds in cinnamon could build up in the body and cause harm, whereas water-soluble compounds are easily excreted.
Cinnamon does still taste good (which might be bad news to dieters), that added flavor might allow you to make food like oatmeal and pancakes taste good with less sugar (good news), like many spices, it's relatively high in antioxdants (good news), it might have a minor positive effect on body composition (good news) but it will not supercharge your metabolism into a calorie burning furnace that sheds pounds like water off duck (sorry).
- Judy McBride, "Cinnamon Extract Spices Up Sugar Metabolism," USDA News and Events, July 24, 2000.
- Pham AQ, Kourlas H, Pham DQ, "Cinnamon supplementation in patients with type 2 diabetes mellitus," Pharmacotherapy, Apr 2007 (vol 27, no. 4), pp. 595-99.
- Dugoua JJ, Seely D, Perri D, Cooley K, Forelli T, Mills E, Koren G, "From type 2 diabetes to antioxidant activity: a systematic review of the safety and efficacy of common and cassia cinnamon bark," Can J Physiol Pharmacol., Sep 2007 (vol. 85, no.9), pp. 837-47.
- Tim N Ziegenfuss, Jennifer E Hofheins, Ronald W Mendel, Jamie Landis and Richard A Anderson, "Effects of a Water-Soluble Cinnamon Extract on Body Composition and Features of the Metabolic Syndrome in Pre-Diabetic Men and Women," Journal of the International Society of Sports Nutrition 2006, 3:45-53.
- The endocrine pancreas -- Endocrinology -- NCBI Bookshelf
- Solomon TP, Blannin AK, "Changes in glucose tolerance and insulin sensitivity following 2 weeks of daily cinnamon ingestion in healthy humans", Eur J Appl Physiol. Jan 22, 2009.
- Health Benefits of Cinnamon Extracts (USDA Video)