Introduction
There are some epidemiological markers to the fact that antioxidants may act as slimming aids, but in a scientific study of the subject a good starting point is the paper by Chrysohoou et al., Nutr. Metab. Cardiovasc. Diseases. 17 (8), 590-597, 2007. entitled "The implications of obesity on the total antioxidant capacity in apparently healthy men and women: The ATTICA study. Data from approximately 3000 subjects (approx. 50% male/female) taken from the ATTICA study in Greece were analysed. They concluded that there was an inverse relationship between body fat, central adiposity and (serum total) antioxidant capacity. From the viewpoint of slimming aids, this suggests that a diet high in antioxidants may correlate with lower body weight and a narrower waist.
Because obesity is a major factor in metabolic syndrome; others being hypertension, high blood sugar, high blood pressure, triglycerides, high density lipid cholesterol and BMI, leading to heart disease, stroke, etc., it is apposite to take metabolic syndrome as the all embracing title for this analysis.
Thus, this page is about slimming to reduce weight - and to reduce the risk of heart disease, diabetes and stroke.
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Background

As antinutrients
As with the effect of astringent antioxidants on salivary composition, the importance of antioxidants in the reduction of obesity, again revolves around the polyphenols, in particular the astringent tannins and their tendency to occlude essential nutrients present in the same meal. As the evidence for this apparent conflict with their therapeutic value is published, it will be reported here.

As satiety inducers
In animal studies it has been reported that antioxidant extracts given before a meal can reduce appetite, lowering food intake.
Reference: A.L. Molan et al., Food Chem., 107 (3), 1039-1044, 2007
When human studies are published, the results will be summarised here.
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Human Nutrition
It is a fact that the polyphenol antioxidants increase the TAC value of blood plasma, which is thought to contribute to the protection of the body against ROS and hence oxidative stress. At the same time they can reduce the vitamin and mineral level, themselves antioxidants, by complexation to a non-absorbable form. So, why are these astringent polyphenols so popular as food-based antioxidants? Truth is we do not know, exactly. A recent study of certain condensed tannin-containing food extracts found a positive relationship between the sensation of astringency index (SAI), the human salivary protein precipitation capacity (HSP) and their total antioxidant activity (TAA).
Reference: R. Amarowicz et al., J. Food Lipids. 15 , 28-41, 2008.
These observations set the scene for a possible new area for debate. This is not for the first time in trying to explain the action of antioxidant mechanisms that a delicate balance of roles is encountered, cf. antioxidant-proxidant status.
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Examples of antioxidant slimming aid
1. Catechins in green tea
In a 12 week double-blind study, 35 healthy Japanese men (two groups of 17 and 18) took either 690 mg catechins (green tea extract) or 22 mg (control group) in oolong tea. Body weight, BMI, waist measurement were all lower after 12 weeks for the green tea extract group.
Reference: T. Nagao et al., Am. J. Clin. Nutr. 81 (1), 122-129, 2005
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2. in vitro enzyme inhibition by berry polyphenols
There is evidence that tea, herb and berry polyphenols can inhibit pancreatic lipase activity, thus reducing the digestion of tryglycerides, as an aid to slimming. The authors of the berry work suggest from chromatographic fractions that ellagitannins might be the active components in lingonberry, arctic bramble, cloudberry, strawberry and raspberry the berries providing the most inhibition, but emphasise the need to verify these findings in vivo.
References:
Tea and herb sources:
R. B. Birani and K. K. Bhutani., Drug discovery today. 12, 879-889, 2007.
Berry sources:
G. J. McDougall, et al., Food Chem. 115, 193-199, 2009
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Comparing high and low fruit content of energy-restricted diets
Although no difference in weight loss occurred between a low fruit (5% of the total energy from fruit) and a high fruit (15% total energy from fruit) diet, the high fruit diet improved the oxidative stress status of the obese women on the trial, with the attendant reduction in the cardiovascular disease risk factor related to obesity.
Reference: A B Crujeiras, et al., Nutrition, 22 (6), 593-599, 2006
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