Ah, green tea! Instead of soda, diet soda, etc…
Green Tea has a number of potential benefits for the person seeking to lose or maintain weight. It contains compounds that may reduce appetite and improve insulin sensitivity. In addition, it appears to reduce inflammation; this is important in people who are obese or overweight, because abdominal fat produces a number of chemicals of an inflammatory nature that age us more rapidly. Lastly, these compounds also appear to protect against organ and cellular damage that occurs from inflammation. It has some caffeine (diuretic), so you need to maintain good water intake.
When I arrived at the weight loss center, Structure House, they recommended that participants not drink caffeinated beverages. This was due to their diuretic effects, which would make us dehydrated, given that we were already dieting. However, they did have green tea available (which does have some caffeine in it, though less than regular “black” tea). I drank it to help with caffeine withdrawal. I also found that I enjoyed it. I would often drink it when I was hungry in between meals, and in most cases, my hunger would pass. If not, then I would eat something a half hour later. Over time, I ended up drinking 5-6 cups a day, and interestingly enough, this “dose” is what appears in many of the scientific studies mentioned below.
In time, I have become somewhat of a “tea snob”, traveling with a tea infuser and loose tea, as well as tea bags. While one can certainly buy expensive, gourmet teas, I also enjoy the green tea bags that I buy from Costco. Some of my favorite green teas are:
- Harney’s Gyokuro
- Harney’s Chun Lu
- Two Leaves and a Bud’s Orange Sencha
- Two Leaves and a Bud’s Tamayokucha
- Kirkland (Costco) Signature Green Tea Matcha Blend
While the prices may seem high for tea that weighs very little, in fact the costs of even excellent tea are a good bit less that than the “MochaFrap…” concoctions that pass for coffee these days – which are both both pricey, and full of fat and calories! Besides, leaves can be reused once or twice – see these instructions for brewing green tea.
One caveat: if you drink caffeine-containing beverages too late in the day, it may make it hard to fall asleep and/or stay asleep during the night. Since many overweight and obese people have trouble sleeping anyway; it’s probably best not to drink green tea after 3p or 5p.
What does the scientific literature say?:
What does the scientific literature say?:
Green Tea has a number of potential benefits for the person seeking to lose or maintain weight. It contains compounds that may reduce appetite and improve insulin sensitivity. In addition, it appears to reduce inflammation; this is important in people who are obese or overweight, because abdominal fat produces a number of chemicals of an inflammatory nature that age us more rapidly. Lastly, these compounds also appear to protect against organ and cellular damage that occurs from inflammation.
Compounds in green tea that may have health benefits include caffeine (though less than in black tea or coffee), and a host of polyphenols. Polyphenols have antioxidant properties. The catechins, particularly (-)-epigallocatechin-3-gallate (EGCG) have been the subject of extensive research. While the increased metabolic rate may ahve some small benefit in terms of producing weight loss, appetite suppresant effects are probably more important
Reviews of the effects of green tea and catechins conclude: “Dose-response relationships observed in several epidemiological studies have indicated that pronounced cardiovascular and metabolic health benefits can be obtained by regular consumption of 5-6 or more cups of green tea per day. Furthermore, intervention studies using similar amounts of green tea, containing 200-300 mg of EGCG, have demonstrated its usefulness for maintaining cardiovascular and metabolic health. Additionally, there are numerous in vivo studies demonstrating that green tea and EGCG exert cardiovascular and metabolic benefits in these model systems. Therefore, green tea and EGCG can be regarded as food components useful for the maintenance of cardiovascular and metabolic health.”
Green tea and/or its extracts appear to protect a variety of organs from the ravages of obesity, diabetes, and inflammation. Animal studies highlight this. These organs and systems include the liver, brain, heart, pancreas, and adipose (fat) tissue. Green tea extracts (GTE) are superior to black tea extracts in preventing high blood sugar and cholesterol levels in animals with experimental diabetes and/or obesity. In these studies, GTE also help to prevent the liver damage (and fat infiltration) that is often seen with obesity. Green tea may help the body to absorb less fat from the intestines. Catechin has been shown in animal models to alter the expressions of genes that promote fact accumulation; they ” effectively reduces adipose tissue mass and ameliorates plasma lipid profiles in high-fat diet-induced obese mice. These effects might be at least partially mediated via regulation of the expression of multiple genes involved in adipogenesis, lipolysis, beta-oxidation and thermogenesis in white adipose tissue.”1 Another animal showed that “The results indicate the protective effect of green tea catechin and caffeine on the functions of brain and pancreas in mice fed a high-fat diet.”2 A different animal study concluded that “Our results indicate that long-term EGCG treatment attenuated the development of obesity, symptoms associated with the metabolic syndrome, and fatty liver. Short-term EGCG treatment appeared to reverse preexisting high-fat-induced metabolic pathologies in obese mice. These effects may be mediated by decreased lipid absorption, decreased inflammation, and other mechanisms.”3 4567 Additionally, compounds in green tea have been shown in experimental animal models to limit the tissue damage from low oxygen levels, and better preserve brain function and learning.8 This latter experimental animal model mimics obstructive sleep apnea (OSA), where oxygen levels fall when breathing is interrupted during sleep. Obstructive sleep apnea is much more common in obese people, and is associated with impaired cognitive function in humans, as well.
The continuous ingestion of a GTE high in catechins led to a reduction in body fat, systolic blood pressure (SBP), and LDL cholesterol, suggesting that the ingestion of such an extract contributes to a decrease in obesity and cardiovascular disease risks.9Green tea extracts have been shown to lower blood pressure in humans, and also improve mood.10 They may also raise HDL (“good” cholesterol) and lower triglycerides and LDL (“bad” cholesterol).11 They also increase energy expenditure.12 Studies in people have shown some similar results in randomized control trials.13 These are the “gold standards” for clinical research, where one group of patients gets the treatment and another does not, with the choices made essentially by a “coin-toss.” Patients taking green tea extracts (especially those higher in caffeine and catechins) had better glucose control,14 more weight loss, lower cholesterol levels, and thinner waistlines.1516 When combined with capsaicin (the active ingredient in hot sauce), “a combination of capsaicin and green tea reduced energy intake during positive energy balance. Capsaicin and green tea suppressed hunger and increased satiety more during negative than during positive energy balance.”17
One reviewer concluded that “The number of human studies in this field is still limited. However, the majority of human epidemiological and intervention studies demonstrate beneficial effects of green tea or green tea extracts, rich in EGCG on weight management, glucose control and cardiovascular risk factors. The optimal dose has not yet been established. The current body of evidence in humans warrants further attention. In particular, well-controlled long-term human studies would help to fully understand the protective effects of green tea catechins on parameters related to the MetS.”18
Green tea extracts have been shown to lower blood pressure in humans, and also improve mood.19 They may also raise HDL (“good” cholesterol) and lower triglycerides and LDL (“bad” cholesterol).20 They also increase energy expenditure.21
The continuous ingestion of a GTE high in catechins led to a reduction in body fat, systolic blood pressure (SBP), and LDL cholesterol, suggesting that the ingestion of such an extract contributes to a decrease in obesity and cardiovascular disease risks.22
As is often the case in medicine and clinical research, there are some studies that do not show benefits on energy expenditure or weight loss with green tea.23
PMID = PUBMED ID; go to www.ncbi.nlm.nih.gov/pubmed/ and enter the # in the search bar for the references
1 PMID: 19390166
2 PMID: 18976677
3 PMID: 18716169
4 PMID: 19825205
5 PMID: 18203899
6 PMID: 19262013
7 PMID: 18053305
8 PMID: 18276944
9 PMID: 17557985
10 PMID: 18710606
11 PMID: 18468736
12 PMID: 18006026
13 PMID: 19736596
14 PMID: 19008868
15 PMID: 19074207
16 PMID: 19680234
17 PMID: 19345452
18 PMID: 19147161
19 PMID: 18710606
20 PMID: 18468736
21 PMID: 18006026
22 PMID: 17557985
23 PMID: 16351782