BACKGROUND AND PURPOSE:

• While differences between low-fat and low-carbohydrate diets have been slight, there can be larger variability between those enrolled in a particular diet type
• It has been suggested in previous literature that these differences could be related to
  • Underlying genetic make-up
  • Baseline Insulin dynamics such that individuals with greater insulin resistance may have better success with low-carbohydrate diets
• Gardner et al. (JAMA 2018) examined the effect of healthy low-fat (HLF) diet vs a health low-carbohydrate(HLC) diet on weight change and if genotype pattern or insulin secretion are related to dietary effects on weight loss

METHODS:

• Single-site, parallel-group, randomized trial
• Data collected from The Diet Intervention Examining The Factors Interacting with Treatment Success (DIETFITS) trial
• Participants: Patients 18 to 50 years without diabetes and body mass index between 28 and 40
• Patients were randomized to 12 months of
  • HLF diet
  • HLC diet
• Behavior modification intervention via 22 diet-specific small group sessions
  • Focused on ways to achieve the lowest fat or carbohydrate intake that could maintained over long periods of time
• 3 SNPs (previously identified in weight loss studies) and INS-30 (blood concentration of insulin 30 minutes after a glucose challenge) were tested for association with weight loss
• Primary outcome: 12-month weight change and determination of whether there were significant interactions among diet type and genotype pattern, diet and insulin secretion, and diet and weight loss

RESULTS:

• Data was collected from 609 participants
  • Mean age, 40 years | 57% women | mean BMI, 33
  • 40% had a low-fat genotype and 30% had a low-carbohydrate genotype
  • Mean baseline INS-30, 93 μIU/mL
• In the HLF vs HLC diets, respectively, the mean 12-month macronutrient distributions were 48% vs 30% for carbohydrates, 29% vs 45% for fat, and 21% vs 23% for protein
• There was no significant difference in weight change at 12 months between the two groups
  • −5.3 kg for the HLF diet vs −6.0 kg for the HLC diet (mean between-group difference, 0.7 kg [95% CI, −0.2 to 1.6 kg])
• There was no significant diet-genotype pattern interaction (P = .20) or diet-insulin secretion (INS-30) interaction (P = .47) with 12-month weight loss
• Secondary Findings
  • Blood lipid results
    • HLF group: More favorable LDL cholesterol profile
    • HLC group: More favorable HDL cholesterol and triglyceride profile

CONCLUSION:

• There was no significant change in weight loss between a healthy low-fat and low-carbohydrate diet
• There was no significant interaction between genotype or insulin secretion with weight loss

Learn More – Primary Sources:

Effect of Low-Fat vs Low-Carbohydrate Diet on 12-Month Weight Loss in Overweight Adults and the Association With Genotype Pattern or Insulin Secretion

Related ObG Topics:

PURE Study Results – Carbs vs Fat Intake to Reduce Cardiovascular Morbidity and Mortality?

More From the PURE Study: Does Type of Exercise Matter When it Comes to Decreasing Mortality and CVD?  

Results of the DiRECT Trial: Can Weight Loss in a Primary Care Setting Achieve Remission of Type 2 Diabetes?