Kitabchi 2013.

Study characteristics
Methods	Review comparison(s) addressed by this study: 1 Study design: RCT, parallel, single‐centre (1) Trial registry number: NCT01642849 Total number of trial arms: 2 Year trial started: NR Sample size calculation: Yes Outcome(s) used for sample size calculation: Change in weight Duration of run‐in period (weeks): NA What was the duration of the weight loss phase: 6 months What was the duration of the weight maintenance phase: NA Other notes about methods: ITT approach was not used.
Participants	Country and setting: USA, outpatient clinical research centre at a university in Knoxville. All food required to complete the respective diets were provided, predominantly as frozen foods. Eligibility criteria: Premenopausal women aged 20–50 years with a BMI > 30 to < 55 kg/m2. fasting glucose < 110 mg/dL and 2‐h glucose level < 170 mg/dL. Participants were excluded if they had proteinuria or elevated serum creatinine (> 1.5 mg/dL), surgical or premature menopause, history of liver disease or abnormal liver function tests, diabetes, thyroid disease with abnormal thyrotropin, weight > 350 lbs, triglycerides > 400 mg/dL or LDL cholesterol > 160 mg/dL, systolic blood pressure > 145 mmHg or diastolic blood pressure > 100 mmHg, used medications known to affect lipid or glucose metabolism (niacin, steroids, and statins), were pregnant or wanted to become pregnant in the next six months, had weight loss of > 5% of body weight in the last six months, or had a history of cancer undergoing active treatment. Type 2 diabetes at baseline: No Impaired glucose tolerance at baseline: Unclear Cardiovascular conditions/risk factors/events at baseline: Unclear Gender: Female Total number randomised: 32 Total attrition in trial: 8 Treatment diet Participants randomised: 14 Participants withdrawn (voluntary): 2 Total attrition: 2 Control diet: Participants randomised: 18 Participants withdrawn (voluntary): 6 Total attrition: 6 Baseline data treatment diet: Randomised participants not included: 2/14 Age (years): mean (SE) 35.9 (2.1) Gender distribution (as reported): female 100%, male 0% Weight (kg): NR BMI (kg/m2): mean (SD) 41.3 (6.24) DBP (mmHg): mean (SD) 83 (1.3) SBP (mmHg): mean (SD) 129 (1.5) HbA1c (%): NR LDL (mmol/L): NR HDL (mmol/L): NR Non‐HDL (mmol/L): NR TC (mmol/L): NR TG (mmol/L): NR Baseline data control diet: Randomised participants not included: 6/18 Age (years): mean (SE) 35.4 (2.0) Gender distribution (as reported): female 100%, male 0% Weight (kg): NR BMI (kg/m2): mean (SD) 37.0 (5.2) DBP (mmHg): mean (SD) 82 (1.4) SBP (mmHg): mean (SD) 128 (1.7) HbA1c (%): NR LDL (mmol/L): NR HDL (mmol/L): NR Non‐HDL (mmol/L): NR TC (mmol/L): NR TG (mmol/L): NR Group differences at baseline: no Characteristic(s) with significant group difference and relevant statistic: NA Other notes about participants: Only the baseline characteristics for completers (12 in intervention and 12 in control group) were reported.
Interventions	Energy (E) comparison of treatment vs control diets: Similar energy prescription/approach to restrict energy intake in both diets Treatment diet: Name (as reported) and brief description: High‐protein low‐carbohydrate (HP) diet, 40% carbohydrates, 30% fat and 30% protein. Energy prescription 500 kcal/day from calculated maintenance needs established by resting energy expenditure Treatment diet type (carbohydrate‐fat‐protein): Low‐balanced‐high Exercise component? No Recipients: N = 12 women with a mean (SE) age of 35.9 (2.1) years and mean (SE) BMI of 41.3 (1.8) kg/m2 with no history of diabetes or prediabetes Why? A hypocaloric high‐protein diet may result in the suppression of hunger and induction of satiety, resulting in weight loss. It may also result in a positive nitrogen balance, therefore assisting in the maintenance of lean body mass, compared to a hypocaloric high‐carbohydrate diet. Furthermore, it may have positive effects on metabolic parameters, such as b‐cell function, cardiovascular risk factors, oxidative stress, and lipid peroxidation. What (materials)? At baseline, an individualised weekly food diary (which included the participant’s preferences) was printed and given to each subject with instructions for recording all food intake on a daily basis. Weekly provision of fresh, prepackaged, and frozen foods for the duration of the study. Most of the entrees for the diet were frozen entrees purchased directly from the manufacturer. The diet included 1 cup of frozen vegetables at both lunch and dinner. Snacks in between meals included shakes and meal bars. Participants were given all food needed to meet their dietary assignment for the duration of the study. All food was dispensed by the dietitian at the CRC on a weekly basis to each participant. An individualised weekly food diary (which included the participant’s preferences) was printed and given to each subject with instructions for recording all food intake on a daily basis. What (procedures)? High‐protein (40% carbohydrates, 30% fat, and 30% protein) hypocaloric diet for 6 months. Weight reduction caloric needs were established for each individual by subtracting 500 kcal/day from their calculated maintenance needs established by REE. Weight loss of 1–2 lbs weekly was targeted. On average, an 1800 kcal/day diet for a 70‐kg individual was used to achieve adequate weight loss. If a subject reached a plateau and did not lose weight for two consecutive weeks, calories were reduced by an additional 200 kcal or to a minimum of 1200 kcal/day. Caloric adjustments were made by altering the amount of supplement bars and/or shakes. Since these were very similar to the nutrient composition of each diet, they could be easily taken out of the diet to reduce calories but maintain adequate nutrient composition. The study diets provided more than the recommended amount of calcium (1000 mg/day) for women 20–50 years of age by providing an average of 1725 mg for HC and 1684 mg for HP diets. Both HP and HC diets were designed to minimise participant health risks. Dietary fat sources focussed on monounsaturated and polyunsaturated fats, i.e. plant oils, semi‐liquid margarine, and nuts; dietary carbohydrate sources emphasised whole grains, fruits, vegetables, and legumes; and dietary protein sources included lean meats, fish, chicken, eggs, and nonfat dairy foods, i.e. fat‐free milk and low‐fat cheese, consistent with American Diabetes Association and Institute of Medicine guidelines. Who provided? Dietitian How and where? "All participants were seen in the Clinical Research Center (CRC) at the University of Tennessee Health Science Center for all their visits." When and how much? Every week for 24 weeks. If a participant did not lose weight for two consecutive weeks, calories were reduced by an additional 200 kcal or to a minimum of 1200 kcal/day altering the amount of supplement bars and/or shakes provided. Strategies to improve or maintain fidelity; tailoring and modification: Subjects were asked to turn in completed food diaries each week in order to pick up the next week’s food. At times, the dietitian adjusted the participant’s meal choices if issues arose regarding compliance. Studies have shown increased dietary compliance with frequent interaction, an individualised diet with food variety, and some form of food recording system. The study dietitian assessed compliance by both subjective and objective parameters including weekly individual contact with patients that included a detailed review of their food diaries. Extent of intervention fidelity: Compliance mean (SE) 94 (1.5)% Concomitant interventions: NR Control diet: Name (as reported) and brief description: High‐carbohydrate low‐protein (HC) diet, 55% carbohydrates, 30% fat and 15% protein. Energy prescription 500 kcal/day from calculated maintenance needs established by resting energy expenditure Control diet type (carbohydrate‐fat‐protein): Balanced‐balanced‐balanced Exercise component? No Recipients: N = 12 women with a mean (SE) age of 35.4 (2.0) years and mean (SE) BMI of 37.0 (1.5) kg/m2 with no history of diabetes or prediabetes Why? A hypocaloric high‐protein diet may result in the suppression of hunger and induction of satiety, resulting in weight loss. It may also result in a positive nitrogen balance, therefore assisting in the maintenance of lean body mass, compared to a hypocaloric high‐carbohydrate diet. Furthermore, it may have positive effects on metabolic parameters, such as b‐cell function, cardiovascular risk factors, oxidative stress, and lipid peroxidation. What (materials)? At baseline, an individualised weekly food diary (which included the participant’s preferences) was printed and given to each subject with instructions for recording all food intake on a daily basis. Weekly provision of fresh, prepackaged, and frozen foods for the duration of the study. Most of the entrees for the diet were frozen entrees purchased directly from the manufacturer. The diet included 1 cup of frozen vegetables at both lunch and dinner. Snacks in between meals included shakes and meal bars. Participants were given all food needed to meet their dietary assignment for the duration of the study. All food was dispensed by the dietitian at the CRC on a weekly basis to each participant. An individualised weekly food diary (which included the participant’s preferences) was printed and given to each subject with instructions for recording all food intake on a daily basis. What (procedures)? "High‐carb (55% carbohydrates, 30% fat, and 15% protein) hypocaloric diet for 6 months. Weight reduction caloric needs were established for each individual by subtracting 500 kcal/day from their calculated maintenance needs established by REE. Weight loss of 1–2 lbs weekly was targeted. On average, an 1800 kcal/day diet for a 70‐kg individual was used to achieve adequate weight loss. If a subject reached a plateau and did not lose weight for two consecutive weeks, calories were reduced by an additional 200 kcal or to a minimum of 1200 kcal/day. Caloric adjustments were made by altering the amount of supplement bars and/or shakes. Since these were very similar to the nutrient composition of each diet, they could be easily taken out of the diet to reduce calories but maintain adequate nutrient composition. The study diets provided more than the recommended amount of calcium (1000 mg/day) for women 20–50 years of age by providing an average of 1725 mg for HC and 1684 mg for HP diets. Both HP and HC diets were designed to minimise participant health risks. Dietary fat sources focussed on monounsaturated and polyunsaturated fats, i.e. plant oils, semi‐liquid margarine, and nuts; dietary carbohydrate sources emphasised whole grains, fruits, vegetables, and legumes; and dietary protein sources included lean meats, fish, chicken, eggs, and nonfat dairy foods, i.e. fat‐free milk and low‐fat cheese, consistent with American Diabetes Association and Institute of Medicine guidelines." Who provided? Dietitian How and where? "All participants were seen in the Clinical Research Center (CRC) at the University of Tennessee Health Science Center for all their visits." When and how much? Every week for 24 weeks. If a participant did not lose weight for two consecutive weeks, calories were reduced by an additional 200 kcal or to a minimum of 1200 kcal/day altering the amount of supplement bars and/or shakes provided. Strategies to improve or maintain fidelity; tailoring and modification: Subjects were asked to turn in completed food diaries each week in order to pick up the next week’s food. At times, the dietitian adjusted the participant’s meal choices if issues arose regarding compliance. Studies have shown increased dietary compliance with frequent interaction, an individualised diet with food variety, and some form of food recording system. The study dietitian assessed compliance by both subjective and objective parameters including weekly individual contact with patients that included a detailed review of their food diaries. Extent of intervention fidelity: Compliance mean (SE) 9 (4.8)% Concomitant interventions: NR
Outcomes	Change in body weight (kg) at 3 to < 12 months: No Change in body weight (kg) at ≥ 12 months: No Number of participants with 5% weight loss from baseline at 3 to < 12 months: No Number of participants with 5% weight loss from baseline at ≥ 12 months: No Change in BMI (kg/m2) at 3 to 12 months: Yes Change in BMI (kg/m2) at ≥ 12 months: No Number of participants with 5% BMI reduction from baseline at 3 to 12 months: No Number of participants with 5% BMI reduction from baseline at ≥ 12 months: No Change in DBP (mmHg) at ≥ 12 months: No Change in SBP (mmHg) at ≥ 12 months: No All‐cause mortality at ≥ 12 months: No Cardiovascular mortality at ≥ 12 months: No Non‐fatal myocardial infarction at ≥ 12 months: No Non‐fatal stroke at ≥ 12 months: No Diagnosis of type 2 diabetes mellitus at ≥ 12 months: No Change in HbA1c (%) at ≥ 12 months: No Change in LDL (mmol/L) at ≥ 12 months: No Change in HDL (mmol/L) at ≥ 12 months: No Change in non‐HDL (mmom/L) at ≥ 12 months: No Change in total cholesterol (TC) (mmol/L) at ≥ 12 months: No Change in triglycerides (or triacylglycerides) (TG) (mmol/L) at ≥ 12 months: No Participant‐reported adverse effects: No
Notes	Number and type of records(s): journal article Trial acronym/name: None Trial funded by: American Diabetes Association (grant 1‐09‐CR‐32) Declaration of interest: "No potential conflicts of interest relevant to this article were reported."