Popular Diets Study

• resting energy expenditure using indirect calorimetry in the fasting state [ Time Frame: end of each dietary period ] [ Designated as safety issue: No ]
• insulin resistance assessed by frequently-sampled oral glucose tolerance test [ Time Frame: end of each dietary period ] [ Designated as safety issue: No ]
• thyroid function tests [ Time Frame: end of each dietary period ] [ Designated as safety issue: No ]

• resting energy expenditure using indirect calorimetry in the fasting state
• insulin resistance assessed by frequently-sampled IV glucose tolerance test
• thyroid function tests

• total energy expenditure using doubly labeled water methodology [ Time Frame: end of each dietary period ] [ Designated as safety issue: No ]
• thermic effect of food using indirect calorimetry [ Time Frame: end of each dietary period ] [ Designated as safety issue: No ]
• physical activity using accelerometry [ Time Frame: end of each dietary period ] [ Designated as safety issue: No ]
• serum lipids [ Time Frame: end of each dietary period ] [ Designated as safety issue: No ]
• plasminogen activator inhibitor-1 [ Time Frame: end of each dietary period ] [ Designated as safety issue: No ]
• C-reactive protein [ Time Frame: end of each dietary period ] [ Designated as safety issue: No ]
• blood pressure [ Time Frame: end of each dietary period ] [ Designated as safety issue: No ]
• hunger/appetite [ Time Frame: end of each dietary period ] [ Designated as safety issue: No ]
• insulin 30 minutes after oral glucose (as an effect modifier) [ Time Frame: baseline ] [ Designated as safety issue: No ]
• Core temperature [ Time Frame: End of each dietary period ] [ Designated as safety issue: No ]
• secreted frizzle-related protein-4 [ Time Frame: end of each dietary period ] [ Designated as safety issue: No ]
• heme-oxygenase [ Time Frame: end of each dietary period ] [ Designated as safety issue: No ]
• Irisin [ Time Frame: end of each dietary period ] [ Designated as safety issue: No ]
• fibroblast growth factor-21 [ Time Frame: end of each dietary period ] [ Designated as safety issue: No ]
• chemerin [ Time Frame: end of each dietary period ] [ Designated as safety issue: No ]
• trimethylamine N-oxide [ Time Frame: fasting and postprandial, end of each dietary period ] [ Designated as safety issue: No ]
• alanine aminotransferase [ Time Frame: end of each dietary period ] [ Designated as safety issue: No ]
• Uric acid [ Time Frame: end of each dietary period ] [ Designated as safety issue: No ]
• insulin [ Time Frame: fasting and postprandial, end of each dietary period ] [ Designated as safety issue: No ]
• ghrelin [ Time Frame: fasting and postprandial, end of each dietary period ] [ Designated as safety issue: No ]
• gastric inhibitory peptide [ Time Frame: fasting and postprandial, end of each dietary period ] [ Designated as safety issue: No ]
• GLP1 [ Time Frame: fasting and postprandial, end of each dietary period ] [ Designated as safety issue: No ]
• PYY [ Time Frame: fasting and postprandial, end of each dietary period ] [ Designated as safety issue: No ]
• Amylin [ Time Frame: fasting and postprandial, end of each dietary period ] [ Designated as safety issue: No ]
• Leptin [ Time Frame: end of each dietary period ] [ Designated as safety issue: No ]

• total energy expenditure using doubly labeled water methodology
• thermic effect of food using indirect calorimetry
• physical activity using accelerometry
• serum lipids
• plasminogen activator inhibitor-1
• C-reactive protein
• blood pressure
• other hormones (in addition to thyroid-related hormones)
• hunger/appetite

The aim of this study is to evaluate the effects of three dominant dietary patterns - conventional low-fat, low-glycemic index (GI) and very-low-carbohydrate - on energy metabolism and heart disease risk factors following weight loss in obese young adults in a feeding study

For most of the last half century, reduction in fat intake has been the primary nutritional approach for the prevention and treatment of obesity and cardiovascular disease (CVD). Over the last few years, very low carbohydrate (Atkins-type) diets have achieved great popularity, with publication of several studies suggesting greater weight loss and improvements in CVD risk factors over 3 to 6 months. Recently, a third dietary approach focused on glycemic index (GI) has generated interest. However, few studies have compared the effects of these diets on body weight regulation and risk for CVD. The primary hypotheses of this study are that any diet that lowers the postprandial rise in blood glucose (very-low-carbohydrate or low-GI) will have beneficial effects on the physiological adaptations to weight loss and on some CVD risk factors. However, other CVD risk factors will be adversely affected by a very-low-carbohydrate vs. a low-GI diet. Preliminary data provide strong support for these hypotheses, by showing that resting energy expenditure declines less and CVD risk factors improve more with weight loss on a low-glycemic load diet compared to a conventional low-fat diet. This application proposes a cross-over feeding design to study the effects of three diets following 12.5% weight loss in obese young adult subjects (n = 24, age 18 to 40 years). The diets are: 1) conventional low-fat, with 60% carb, 20% fat, 20% protein; 2) low-GI with 40% carb, 40% fat, 20% protein; and 3) very-low-carbohydrate with 10% carb, 60% fat, 30% protein. The primary outcome is resting energy expenditure (indirect calorimetry). Secondary outcomes include total energy expenditure (doubly labeled water), thermic effect of food (indirect calorimetry), physical activity (accelerometry), insulin resistance and B-cell function (frequently-sampled OGTT), blood lipids, blood pressure and measures of systemic inflammation and coagulopathy. This study should have major public health implications to the millions of Americans currently following diets to decrease body weight and risk for heart disease.

• Obesity
• Insulin Resistance

• Other: Low glycemic index diet
  Feeding protocol, all foods prepared in a metabolic kitchen
• Other: Low fat diet
  Feeding protocol, all foods prepared in a metabolic kitchen
• Other: Very low carbohydrate diet
  Feeding protocol, all foods prepared in a metabolic kitchen

• Experimental: 1
  Low glycemic index diet
  Intervention: Other: Low glycemic index diet
• Active Comparator: 2
  Low fat diet
  Intervention: Other: Low fat diet
• Active Comparator: 3
  Very low carbohydrate diet
  Intervention: Other: Very low carbohydrate diet

• Walsh CO, Ebbeling CB, Swain JF, Markowitz RL, Feldman HA, Ludwig DS. Effects of Diet Composition on Postprandial Energy Availability during Weight Loss Maintenance. PLoS One. 2013;8(3):e58172. doi: 10.1371/journal.pone.0058172. Epub 2013 Mar 6.
• Ebbeling CB, Swain JF, Feldman HA, Wong WW, Hachey DL, Garcia-Lago E, Ludwig DS. Effects of dietary composition on energy expenditure during weight-loss maintenance. JAMA. 2012 Jun 27;307(24):2627-34.

Inclusion Criteria:

• BMI ≥ 27 kg/m2
• Willing and able to come to the GCRC 5 days per week to consume a supervised meal and pick-up food for all other meals
• Available for scheduled hospital admissions
• Willing to abstain from alcohol consumption for the duration of the study
• If female, regular menstrual cycles (defined as 26 to 30 days between cycles; no more than one day variation in the duration of menstrual flow)

Exclusion Criteria:

• Weight > 350 lbs
• Change in body weight (± 10%) over preceding year
• Taking any medications or dietary supplements that might affect body weight, appetite, or energy expenditure
• Smoking (1 cigarette in the last week)
• High levels of physical activity
• Currently following a special diet
• Abnormal laboratory screening tests
• Type 2 diabetes mellitus
• Allergies or aversions to foods on the study menu
• Previous diagnosis of an eating disorder or any other mental health disorder
• If female, pregnant in the past 12 months or planning to become pregnant during the study period
• If female, lactating in the preceding 12 months
• If taking birth control medication, change in medication in previous 3 months or plans to change medication during the study period

• National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
• Brigham and Women's Hospital