Despite being a long known spice and its known role in traditional medicine the modern evidence for health related benefits and detriments of cinnamon are sparse.The NCCIH sums it up with NCCIH Publication No.463: Cinnamon:
Studies done in people don’t support using cinnamon for any health
condition.
Cinnamon is indeed used in the way the OP phrased it, but whether it is really effective remains currently dubious.
Results in Favour of Cinnamon
There are some scientific studies showing very interesting and promising results like:
Improved Insulin Resistance and Lipid Metabolism by Cinnamon Extract through Activation of Peroxisome Proliferator-Activated Receptors
Peroxisome proliferator-activated receptors (PPARs) are
transcriptional factors involved in the regulation of insulin
resistance and adipogenesis. Cinnamon, a widely used spice in food
preparation and traditional antidiabetic remedy, is found to activate
PPAR and , resulting in improved insulin resistance, reduced fasted
glucose, FFA, LDL-c, and AST levels in high-caloric diet-induced
obesity (DIO) and mice in its water extract form. In vitro studies
demonstrate that cinnamon increases the expression of peroxisome
proliferator-activated receptors and (PPAR/) and their target genes
such as LPL, CD36, GLUT4, and ACO in 3T3-L1 adipocyte. The
transactivities of both full length and ligand-binding domain (LBD) of
PPAR and PPAR are activated by cinnamon as evidenced by reporter gene
assays. These data suggest that cinnamon in its water extract form can
act as a dual activator of PPAR and , and may be an alternative to
PPAR activator in managing obesity-related diabetes and
hyperlipidemia.
Cinnamon polyphenols regulate multiple metabolic pathways involved in insulin signaling and intestinal lipoprotein metabolism of small intestinal enterocytes
Results
Ex vivo, the cinnamon extract significantly decreased the amount of
apolipoprotein-B48 secretion into the media, inhibited the mRNA
expression of genes of the inflammatory cytokines, interleukin-1β,
interleukin-6, and tumor necrosis factor-α, and induced the expression
of the anti-inflammatory gene, Zfp36. CE also increased the mRNA
expression of genes leading to increased insulin sensitivity,
including Ir, Irs1, Irs2, Pi3k, and Akt1, and decreased Pten
expression. CE also inhibited genes associated with increased
cholesterol, triacylglycerols, and apolipoprotein-B48 levels,
including Abcg5, Npc1l1, Cd36, Mttp, and Srebp1c, and facilitated
Abca1 expression. CE also stimulated the phospho-p38 mitogen-activated
protein kinase, c-Jun N-terminal kinase, and
extracellular-signal-regulated kinase expressions determined by flow
cytometry, with no changes in protein levels.
Conclusions
These results demonstrate that the CE regulates genes associated with
insulin sensitivity, inflammation, and cholesterol/lipogenesis
metabolism and the activity of the mitogen-activated protein kinase
signal pathway in intestinal lipoprotein metabolism.
Cinnamon: Potential Role in the Prevention of Insulin Resistance, Metabolic Syndrome, and Type 2 Diabetes
Metabolic syndrome is associated with insulin resistance, elevated
glucose and lipids, inflammation, decreased antioxidant activity,
increased weight gain, and increased glycation of proteins. Cinnamon
has been shown to improve all of these variables in in vitro, animal,
and/or human studies. In addition, cinnamon has been shown to
alleviate factors associated with Alzheimer's disease by blocking and
reversing tau formation in vitro and in ischemic stroke by blocking
cell swelling. In vitro studies also show that components of cinnamon
control angiogenesis associated with the proliferation of cancer
cells. Human studies involving control subjects and subjects with
metabolic syndrome, type 2 diabetes mellitus, and polycystic ovary
syndrome all show beneficial effects of whole cinnamon and/or aqueous
extracts of cinnamon on glucose, insulin, insulin sensitivity, lipids,
antioxidant status, blood pressure, lean body mass, and gastric
emptying. However, not all studies have shown positive effects of
cinnamon, and type and amount of cinnamon, as well as the type of
subjects and drugs subjects are taking, are likely to affect the
response to cinnamon. In summary, components of cinnamon may be
important in the alleviation and prevention of the signs and symptoms
of metabolic syndrome, type 2 diabetes, and cardiovascular and related
diseases.
Metabolism Accelerator?
The most promising indicators going into the direction of the question's "metabolism acceleration" might be found in studies like these:
Cinnamaldehyde induces fat cell-autonomous thermogenesis and metabolic reprogramming:
CA activates thermogenic and metabolic responses in mouse and human primary subcutaneous adipocytes in a cell-autonomous manner, giving a mechanistic explanation for the anti-obesity effects of CA observed previously and further supporting its potential metabolic benefits on humans. Given the wide usage of cinnamon in the food industry, the notion that this popular food additive, instead of a drug, may activate thermogenesis, could ultimately lead to therapeutic strategies against obesity that are much better adhered to by participants.
Inconclusive Results
But trying to gain a systematic view on such a complex substance is quite a challenge.
The Cochrane Library concludes in Cinnamon for diabetes mellitus:
There is insufficient evidence to support the use of cinnamon for type
1 or type 2 diabetes mellitus. Further trials, which address the
issues of allocation concealment and blinding, are now required. The
inclusion of other important endpoints, such as health-related quality
of life, diabetes complications and costs, is also needed.
Another 2011 Research Summary:
One fairly well-studied supplement used to help hyperglycemia in diabetics is cassia cinnamon. Animal and laboratory studies have indicated that cinnamon may mimic the effects of insulin and make cells more sensitive to insulin (Anderson et al., 2004).
In diabetic patients, some studies have shown a favorable response; some no effect. The most comprehensive review of cinnamon use in diabetics, published in 2008 by the journal Diabetes Care (Baker et al., 2008), found no metabolic benefits to the use of cinnamon by type I or type II diabetics. Specifically, no benefits to fasting blood glucose, lipids, or cholesterol were observed in a meta-analysis of five small clinical trials. [Ronald Ross Watson and Victor R. Preedy: "Bioactive Food As Dietary Interventions For Diabetes", Academic Press: San Diego, London, 2013, p377.]
Whereas an article in Annals of Family Medicine sees it in more positive light:
Cinnamon use in type 2 diabetes: an updated systematic review and meta-analysis.
The consumption of cinnamon is associated with a statistically
significant decrease in levels of fasting plasma glucose, total
cholesterol, LDL-C, and triglyceride levels, and an increase in HDL-C
levels; however, no significant effect on hemoglobin A1c was found.
The high degree of heterogeneity may limit the ability to apply these
results to patient care, because the preferred dose and duration of
therapy are unclear.
Summary
Please note that most of the positive results where obtained in beakers and rats, while studies of its effect in humans are mostly either negative, not replicated or inconclusive. Citing a single study that is not a fundamental and large breakthrough is usually a good indication that the newspapers have filled their bogus pipeline.
The effect on metabolic rate seems to be out of focus for the interest in cinnamon and its most promising fields of application as a medicine are directed to diabetes and metabolic syndrome. Whether those sources cited by the OP have any background in valid and reliable scientific evidence seems unlikely. More likely is that they are all examples of 'journalism' (this is meant as an insult) and bad science communication: Taking preliminary findings and blowing them out of proportion, misrepresenting the facts given to them.
Cinnamon in moderation as a spice is nice. If used as an agreeable herb that makes fibrous ingredients more attractive without adding much calories it is superb. If taken as a medicine or supplement it can be quite ineffective and at the same time dangerous. This is especially true if one does not differentiate between cinnamon and cassia. If using large amounts of cinnamon might still be a goal then there are some more things to consider:
How much cinnamon is too much?
