NCT00846040

Reduced Carbohydrate Versus Fat in Obese Subjects

Completed Phase 2 Results posted Last updated 15 April 2021

What this trial tests

Phase 2 trial testing Reduced fat diet in Obesity in 43 participants. Completed in 20 October 2014.

Timeline

13 February 2009

Primary endpoint
24 February 2014

20 October 2014

Quick facts

Lead sponsor	National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Phase	Phase 2
Status	Completed
Study type	INTERVENTIONAL
Allocation	randomized
Design	crossover
Masking	none
Primary purpose	treatment
Enrollment	43
Start date	13 February 2009
Primary completion	24 February 2014
Estimated completion	20 October 2014
Sites	1 location across United States

Drugs / interventions tested

• Reduced fat diet
• Reduced carbohydrate diet
• Drug: f-18 fallypride — full drug profile →
• fMRI — full drug profile →
• PET — full drug profile →

Conditions studied

• Obesity — all drugs for Obesity →

Sponsor

National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)

Who can join

Adults 18 to 45, any sex, with Obesity. Patients with the condition only — healthy volunteers not accepted.

Results — posted to ClinicalTrials.gov

Per-arm endpoint measurements with 95% confidence intervals where reported. Source: trial results section.

Change in Respiratory Quotient (RQ) Primary · Baseline and day 14

Respiratory quotient was calculated as the ratio of carbon dioxide production to oxygen consumption as measured in a metabolic chamber for at least 23 continuous hours on days 2 and 5 of the baseline diet and days 1, 4, and 6 of the reduced-energy diets.

Group	Value	95% CI
RC Diet	-0.0552	± 0.003
RF Diet	0.00453	± 0.003

Change in 24 Hour Energy Expenditure Secondary · Baseline and 14 days

24 hour energy expenditure was measured in a respiratory chamber.

Group	Value	95% CI
RC Diet	-97.7	± 23
RF Diet	-49.6	± 24

Change in Cumulative Fat Imbalance Secondary · Baseline and 14 days

Measured as the difference between dietary fat intake and fat oxidation by the body as measured in the respiratory chamber

Group	Value	95% CI
RC Diet	-245	± 21
RF Diet	-463	± 37

Caudate Dopamine D2-like Receptor Binding Potential (D2BP) Secondary · Day 2 of in-patient admission

The time-activity curves for \[18F\]fallypride tracer concentration in the ROIs were measured by PET and kinetic parameters were fit to a four compartment mathematical model (with the cerebellum used as the reference tissue). D2BP was expressed as the dimensionless ratio of rate constants quantifying binding and unbinding of tracer in the regions of interest.

Group	Value	95% CI
Obese	28.2	26.48 – 29.86
Lean Control	24.9	22.95 – 26.92

Putamen Dopamine D2-like Receptor Binding Potential (D2BP) Secondary · Day 2 of in-patient admission

The time-activity curves for \[18F\]fallypride tracer concentration in the ROIs were measured by PET and kinetic parameters were fit to a four compartment mathematical model (with the cerebellum used as the reference tissue). D2BP was expressed as the dimensionless ratio of rate constants quantifying binding and unbinding of tracer in the regions of interest.

Group	Value	95% CI
Obese	30.7	28.61 – 32.7
Lean Control	27	25.14 – 28.93

Accumbens Dopamine D2-like Receptor Binding Potential (D2BP) Secondary · Day 2 of in-patient admission

The time-activity curves for \[18F\]fallypride tracer concentration in the ROIs were measured by PET and kinetic parameters were fit to a four compartment mathematical model (with the cerebellum used as the reference tissue). D2BP was expressed as the dimensionless ratio of rate constants quantifying binding and unbinding of tracer in the regions of interest.

Group	Value	95% CI
Obese	18.3	16.6 – 19.94
Lean Control	16.7	14.16 – 19.29

Sponsor's own description

Popular weight loss strategies often involve reducing an individual's consumption of carbohydrates or fat. However, no controlled study has been carried out to evaluate the effects of reducing carbohydrate versus fat consumption while keeping the other nutrients at standard levels to maintain an individual's weight. Researchers are interested in investigating how different restrictions of carbohydrates or fats affect the many processes involved in weight loss, including brain activity and blood and brain chemical composition.

Publications & conference data

5 peer-reviewed publications reference this trial (live from Europe PMC):

1. Calorie for Calorie, Dietary Fat Restriction Results in More Body Fat Loss than Carbohydrate Restriction in People with Obesity.
   Hall KD, Bemis T, Brychta R, Chen KY, et al · · 2015 · cited 190× · PMID 26278052 · DOI 10.1016/j.cmet.2015.07.021
2. Striatal dopamine D2-like receptor correlation patterns with human obesity and opportunistic eating behavior.
   Guo J, Simmons WK, Herscovitch P, Martin A, et al · · 2014 · cited 117× · PMID 25199919 · DOI 10.1038/mp.2014.102
3. Nutritional systems biology modeling: from molecular mechanisms to physiology.
   de Graaf AA, Freidig AP, De Roos B, Jamshidi N, et al · · 2009 · cited 45× · PMID 19956660 · DOI 10.1371/journal.pcbi.1000554
4. Dietary fat restriction affects brain reward regions in a randomized crossover trial.
   Darcey VL, Guo J, Courville AB, Gallagher I, et al · · 2023 · cited 10× · PMID 37345661 · DOI 10.1172/jci.insight.169759
5. Automatic engagement of limbic and prefrontal networks in response to food images reflects distinct information about food hedonics and inhibitory control.
   Avery JA, Carrington M, Ingeholm JE, Darcey V, et al · · 2025 · cited 2× · PMID 39979602 · DOI 10.1038/s42003-025-07704-w