CALIBER Phase 1: A Pilot Study in Normal-weight and Overweight Adults.

Pilot study to compare the impact of following a low-carbohydrate, high-fat diet versus following a high-carbohydrates, moderate-fat diet (UK dietary guidelines) on cardiometabolic risk markers and associated behaviours in a normal-weight and overweight adult population.

Cardiometabolic diseases (CMD), such as type 2 diabetes and cardiovascular disease (CVD), are globally amongst the highest contributors to morbidity and mortality with high (cost) implications to the overall economy and health care systems. A number of risk markers have been associated with CMDs, including blood serum markers, low levels of lean mass and high levels of body fat, including increased waist circumference. Dietary factors and nutritional status have long been linked with specific markers of cardiometabolic (CM) risk. The quantity and quality of dietary carbohydrates has been associated with increased serum triglycerides levels, increased body fat mass, increased waist circumference and visceral fat around the organs in particular. They also seem to increase food cravings. Whilst official dietary guidelines in the UK and elsewhere still recommend a high carbohydrate and low fat diet as standard, these recommendations have increasingly been challenged. Evidence has been mounting that very-low carbohydrate (ketogenic) and low carbohydrate diets can ameliorate CM risk factors, especially when a personalised rather than a one-size-fits-all approach is being taken. Response to carbohydrate load and adherence to dietary interventions can vary widely dependent on individual substrate and energy metabolism and insulin-resistant status.

The majority of dietary interventions with ketogenic and low-carbohydrate diets has focused on weight loss as the primary outcome in overweight and obese individuals. However, in recent years evidence has been mounting that the location and quality of adipose tissue (AT) play a more important role in manifestation of CM risk than quantity of AT alone. Detrimental health behaviours, such as low-quality diet and low levels of physical activity seem to be important contributors to this.

Further studies can provide vital insights into the links between diet, location-specific adipose tissue, CM risk factors and health-related behaviours.

Therefore this 8-weeks randomised pilot study will investigate the impact of either following a low-carbohydrate, high-fat diet versus following a high-carbohydrates, moderate-fat diet (UK dietary guidelines) on cardiometabolic risk markers and associated behaviours in a normal-weight and overweight adult population aged 19 - 64 at potential risk of CMD.

Eligibility Criteria:
Inclusion Criteria cohort 1:

1. BMI 18.5 - 29.9kg/m2
2. Aged 19 - 64
3. White-Caucasian
4. Score of ≥4 from a combination of risk markers, including

   * Fasting glucose concentration \>5.5mmol/L = 3 points
   * Waist \>102cm or 40 inches = 2 points (males)
   * Waist \>94 cm or 37 inches = 1 point (males)
   * Waist \>88cm or 34inches = 2 points (females)
   * Waist \>80 cm or 31 inches = 1 point (females)
   * Systolic blood pressure\>130mmHg = 1 point
   * Diastolic BP \>85mmHg = 1 point
   * HDL cholesterol concentration \<1.0mmol/L = 2 points
   * Serum triglyceride concentration \>1.3mmol/L = 1 point.

Exclusion Criteria cohort 1:

1. Smoker
2. Vegetarian or vegan
3. Suffering from food allergies or intolerances
4. Drinking alcohol above recommended UK government guidelines
5. Previous diagnosis of CM disease
6. Taking lipid-lowering medication
7. Taking blood pressure-lowering medication
8. Taking blood glucose-lowering medication
9. Taking dietary supplements
10. Suffering from an eating disorder
11. Current or previous renal impairment

Inclusion Criteria cohort 2:

1. BMI 18.5 - 29.9kg/m2
2. Aged 19 - 64
3. White-Caucasian

Exclusion Criteria cohort 2:

1. Smoker
2. Vegetarian or vegan
3. Suffering from food allergies or intolerances
4. Drinking alcohol above recommended UK government guidelines
5. Previous diagnosis of CM disease
6. Taking lipid-lowering medication
7. Taking blood pressure-lowering medication
8. Taking blood glucose-lowering medication
9. Taking dietary supplements
10. Suffering from an eating disorder
11. Current or previous renal impairment