Lab animals fed the extracts also decreased their food intake by about eight per cent, linked to a satiety effect - boosting the feeling of being full - report the researchers in the journal Food Chemistry .
"The results demonstrated for the first time that rats gavaged daily for six days with one millilitre of extract prepared from 'Maru' and 'Centurion' fruits consumed less food than their counterparts preloaded with the same volume of water," wrote the authors from Massey University (New Zealand) and the University of Illinois at Urbana-Champaign.
If the results can be translated to humans, the berry extracts could find a role in the burgeoning weight loss and management market, estimated to already be worth $7bn (€5.2bn) globally.
Dr Abdul Molan and co-workers used water to obtain antioxidant-rich extracts from the blueberry cultivars 'Centurion' and 'Maru'.
The extracts were then tube-fed to rats (gavaged) at a dose of one millilitre per day for six days.
A group of rats were tube-fed only water as a control.
At the end of the study, the researchers report that blood antioxidant levels, measured using the ferric reducing antioxidant power (FRAP) assay, was significantly increased in both groups fed the blueberry extracts (BBE), compared to the control animals.
The result indicated "that BBE may have the ability to elevate circulating antioxidant potentials in vivo ," they said.
In terms of the satiating effect, the Maru cultivar was associated with an 8.6 per cent decrease in food intake, while Centurion reduced food intake by 6.2 per cent.
Only the former cultivar's effect was 'statistically significant', said the researchers.
The reduction in food intake had a knock-on effect to body weight gain, with rats tube-fed the Maru and Centurion extracts showing 9.2 and 5.3 per cent less gain that control rats, respectively.
"The ability of BBE to reduce the food intake coupled with the decrease in body weight gain compared with their counterparts given water (control group), suggests that BBE may be a good satiety inducer and weight management modulator," wrote Molan.
Mechanism unknown "Although the precise mechanisms which underlie the satiating effects of blueberry extract are not fully understood, it may trigger receptors for amino acids which have been detected in the wall of the upper intestine," wrote the researchers.
"Further studies to investigate the effect underlying mechanisms responsible for the satiating effect are needed," they concluded.
With 50 per cent of Europeans and 62 per cent of Americans classed as overweight, the food industry is waking up to the potential of products for weight loss and management.
The slimming ingredients market can be divided into five groups based on the mechanisms of action - boosting fat burning/ thermogenesis, inhibiting protein breakdown, suppressing appetite/ boosting satiety (feeling of fullness), blocking fat absorption, and regulating mood (linked to food consumption).
Recently, scientists from the USDA Arkansas Children's Nutrition Center and the University of Arkansas reported that purified forms of extracted anthocyanins from berries may decrease obesity, but the whole fruit doesn't produce the same benefits.
The study, performed in mice, was published in the Journal of Agricultural and Food Chemistry (doi: 10.1021/jf071993o).
Source: Food Chemistry (Elsevier) Volume 107, Issue 3, Pages 1039-1044 "Satiety in rats following blueberry extract consumption induced by appetite-suppressing mechanisms unrelated to in vitro or in vivo antioxidant capacity" Authors: A.L. Molan, M.A. Lila, J. Mawson