Effect of Fruit and Vegetables on Insulin Resistance (FIRST)

• Self-reported intake of fruit and vegetables (number of portions per day) [ Time Frame: Start and end of 12 week intervention ] [ Designated as safety issue: No ]
• Cardiovascular risk factors [ Time Frame: Start and end of 12 week intervention ] [ Designated as safety issue: No ]
• Biochemical markers of nutritional status [ Time Frame: Start and end of 12 week intervention ] [ Designated as safety issue: No ]

Current evidence indicates that fruit and vegetable intake and dietary patterns rich in fruit and vegetables may be associated with reduced insulin resistance and may reduce the risk of the metabolic syndrome. If proven, this relationship may partly explain the inverse association between fruit and vegetable intake and cardiovascular disease risk. There are currently no published dietary interventions that have examined in detail the relationship between fruit and vegetable intake and insulin resistance. There is, however, some preliminary evidence from whole diet interventions that a diet rich in fruit and vegetables may have a beneficial effect on insulin resistance. Evidence to date indicates that an investigation of the direct association between fruit and vegetable intakes and insulin resistance in a carefully controlled intervention study is warranted. This study will investigate the dose−response effect of fruit and vegetable intake on insulin resistance in people who are overweight and at high−risk of CVD using state−of−the−art techniques.

• No Intervention: 1
  1-2 portions of fruit and vegetables daily for 12 weeks
  Intervention: Other: Fruit and vegetable intervention
• Active Comparator: 2
  4 portions fruit and vegetables daily for 12 weeks
  Intervention: Other: Fruit and vegetable intervention
• Active Comparator: 3
  7 portions of fruit and vegetables daily for 12 weeks
  Intervention: Other: Fruit and vegetable intervention

Inclusion Criteria:

• BMI between 27-35
• CVD risk >20% over 10 years (using the Joint British Society risk assessment tables)
• Low consumers of fruit and vegetables (<2 portions per day)

Exclusion Criteria:

• Diabetes
• Existing CVD
• Food intolerance/sensitivity preventing adherence to a high fruit and vegetable diet
• Subjects taking antioxidant supplements
• Surgery within the last 3 months
• Pregnancy/lactation
• Aspirin
• Subjects following a weight loss diet