The Effects of Grapefruit on Weight and Insulin Resistance: Relationship to the Metabolic Syndrome

Pennington Biomedical Research Center, Baton Rouge, Louisiana, United States
Journal of Medicinal Food (Impact Factor: 1.7). 02/2006; 9(1):49-54. DOI: 10.1089/jmf.2006.9.49
Source: PubMed

ABSTRACT To study the effects of grapefruit and grapefruit products on body weight and metabolic syndrome, 91 obese patients were randomized to either placebo capsules and 7 ounces (207 mL) of apple juice, grapefruit capsules with 7 ounces (207 mL) of apple juice, 8 ounces (237 mL) of grapefruit juice with placebo capsule, or half of a fresh grapefruit with a placebo capsule three times a day before each meal. Metabolic syndrome parameters were measured at the beginning and end of 12 weeks. After 12 weeks, the fresh grapefruit group had lost 1.6 kg, the grapefruit juice group had lost 1.5 kg, the grapefruit capsule group had lost 1.1 kg, and the placebo group had lost 0.3 kg. The fresh grapefruit group lost significantly more weight than the placebo group (P < .05). A secondary analysis of those with the metabolic syndrome in the four treatment groups demonstrated a significantly greater weight loss in the grapefruit, grapefruit capsule, and grapefruit juice groups compared with placebo (P < .02). There was also a significant reduction in 2-hour post-glucose insulin level in the grapefruit group compared with placebo. Half of a fresh grapefruit eaten before meals was associated with significant weight loss. In metabolic syndrome patients the effect was also seen with grapefruit products. Insulin resistance was improved with fresh grapefruit. Although the mechanism of this weight loss is unknown it would appear reasonable to include grapefruit in a weight reduction diet.

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    • "Of these, an additional 39 articles were excluded for the following reasons: 22 articles did not have the data on outcome measures, 9 articles treated the subjects with multi-component supplement, 8 articles did not report enough details of SD or baseline or endpoint or mean difference for primary or secondary outcome measures [30]–[37]. We contacted the main authors of these 8 studies by email, but only one replied and the requested data was no longer available [31]. Thus, 12 articles were finally selected for inclusion in the meta-analysis [38]–[49]. "
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    ABSTRACT: Diabetes mellitus has become a worldwide health problem. Whether fruit juice is beneficial in glycemic control is still inconclusive. This study aimed to synthesize evidence from randomized controlled trials on fruit juice in relationship to glucose control and insulin sensitivity. A strategic literature search of PubMed, EMBASE, and the Cochrane Library (updated to March, 2014) was performed to retrieve the randomized controlled trials that evaluated the effects of fruit juice on glucose control and insulin sensitivity. Study quality was assessed using the Jadad scale. Weighted mean differences were calculated for net changes in the levels of fasting glucose, fasting insulin, hemoglobin A1c (HbA1c), and homeostatic model assessment of insulin resistance (HOMA-IR) using fixed- or random-effects model. Prespecified subgroup and sensitivity analyses were performed to explore the potential heterogeneity. Twelve trials comprising a total of 412 subjects were included in the current meta-analysis. The numbers of these studies that reported the data on fasting glucose, fasting insulin, HbA1c and HOMA-IR were 12, 5, 3 and 3, respectively. Fruit juice consumption did not show a significant effect on fasting glucose and insulin concentrations. The net change was 0.79 mg/dL (95% CI: -1.44, 3.02 mg/dL; P = 0.49) for fasting glucose concentrations and -0.74 µIU/ml (95% CI: -2.62, 1.14 µIU/ml; P = 0.44) for fasting insulin concentrations in the fixed-effects model. Subgroup analyses further suggested that the effect of fruit juice on fasting glucose concentrations was not influenced by population region, baseline glucose concentration, duration, type of fruit juice, glycemic index of fruit juice, fruit juice nutrient constitution, total polyphenols dose and Jadad score. This meta-analysis showed that fruit juice may have no overall effect on fasting glucose and insulin concentrations. More RCTs are warranted to further clarify the association between fruit juice and glycemic control.
    PLoS ONE 04/2014; 9(4):e95323. DOI:10.1371/journal.pone.0095323 · 3.23 Impact Factor
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    • "The present trial lasted for 9 weeks. Previous trials of grapefruit consumption lasted 12 weeks; however, attrition was relatively high in these studies (15%-20%) [10] [11]. In addition, because of timing and the length of Rio-Red grapefruit crop production, 6 weeks was considered feasible to complete study activities. "
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    ABSTRACT: Folklore has suggested that consuming grapefruit may promote weight control. Sparse data exist to support this hypothesis, although there is some evidence of health promotion effects with regard to blood pressure control and modulation of circulating lipids. The aim of this randomized controlled trial was to prospectively evaluate the role of grapefruit in reducing body weight and blood pressure and in promoting improvements in the lipid profile in overweight adults (N = 74). Following a 3-week washout diet low in bioactive-rich fruits and vegetables, participants were randomized to either the control diet (n = 32) or daily grapefruit (n = 42) in the amount of one half of a fresh Rio-Red grapefruit with each meal (3× daily) for 6 weeks. No differences between group in weight, blood pressure, or lipids were demonstrated. Grapefruit consumption was associated with modest weight loss (-0.61 ± 2.23 kg, P = .097), a significant reduction in waist circumference (-2.45 ± 0.60 cm, P = .0002), and a significant reduction in systolic blood pressure (-3.21 ± 10.13 mm Hg, P = .03) compared with baseline values. Improvements were observed in circulating lipids of those consuming grapefruit, with total cholesterol and low-density lipoprotein significantly decreasing by -11.7 mg/dL (P = .002) and -18.7 mg/dL (P < .001), respectively, compared with baseline values. This study suggests that consumption of grapefruit daily for 6 weeks does not significantly decrease body weight, lipids, or blood pressure as compared with the control condition. However, the improvements in blood pressure and lipids demonstrated in the intervention group suggest that grapefruit should be further evaluated in the context of obesity and cardiovascular disease prevention.
    Metabolism: clinical and experimental 02/2012; 61(7):1026-35. DOI:10.1016/j.metabol.2011.12.004 · 3.61 Impact Factor
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    • "The whole-grain (rich in polyphenols) feeding studies that are available show improvements in biomarkers with whole-grain consumption, such as weight loss and blood lipid improvement [46]. There is evidence that daily intake of some fruits such as three apples or three pears [47;48], or grapefruit (as fresh grapefruit or grapefruit juice or grapefruit capsule) [49], can significantly reduce body weight by 10 or 12 weeks in overweight and obese people independently of the fruit's fiber amount. "
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    ABSTRACT: The relative proportion of Bacteroidetes to Firmicutes is decreased in obese people. This imbalance in gut microbiota generates signals controlling the expression of genes by the epithelial intestinal cells. Both dairy and non-dairy probiotics increase body weight, reportedly through Lactobacillus species growth in the gut. On the other hand, daily intake of some fruits and drinks such as three apples or three pears or grapefruit, or green tea, which all are rich in polyphenols, can significantly reduce body weight in obese people. Metabolism of polyphenols by microbiota involves the cleavage of glycosidic linkages. Glycans, which are the product of glycosidic cleavage, are necessary for survival of the intestinal microbiota as a nutrient foundation. There are two pivotal points: (i) Firmicutes possess a disproportionately smaller number of glycan-degrading enzymes than Bacteroidetes, (ii) Firmicutes are more repressed than the Bacteroidetes by phenolic compounds' antimicrobial properties. The Bacteroidetes community prevails following dietary polyphenol intake and its fermentation to phenolic compounds, due to having more glycan-degrading enzymes, so this may thus be a mechanism by which dietary polyphenols exert their weight lowering effect. I suggest that future studies utilize clone libraries and fingerprinting techniques enabling identification of the composition and community structure of the microbiota, and dot blot hybridization or fluorescent in situ hybridization to analyze abundance of particular taxa in obese and individuals. A supplementation with polyphenols with high bioavailability in obese individuals with higher Firmicutes/Bacteroides community ratio phenotype, when associated to a probiotic restricted diet, is proposed for weight loss; this hypothesis could have relevant implication in planning a successful dietary regimen and/or neutraceutical/pharmaceutical preparations for achieving and maintaining a normal body weight in obese individuals, especially including much more use of polyphenol-rich foodstuffs and/or polyphenol-rich syrups, and including low amounts of probiotic-rich foodstuffs like yogurt, soy yogurt, or as probiotic supplements.
    Chemico-biological interactions 10/2010; 189(1-2):1-8. DOI:10.1016/j.cbi.2010.10.002 · 2.98 Impact Factor
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