Weight loss on low-fat vs. low-carbohydrate diets by insulin resistance status among overweight adults and adults with obesity: a randomized pilot trial.
49
2016
Weight loss on low-fat vs. low-carbohydrate diets by insulin resistance status among overweight adults and adults with obesity: a randomized pilot trial. CD Gardner, LC Offringa, JC Hartle et al. Obesity 2016 volume 24, pp 79-86.
US
1
To research the mediating effects of insulin resistance on weight loss in response to LF vs. LC diets.
61
49
22%
81
6 mo
Y
"Enrolled: 61 adults, divided by IR status BMI: 28-40. Not diabetic, generally healthy Men and women, mean age 40s non-white: 20% 49 completed (80.3%)"
49
"Subjects divided by IR status using proxy measure and then randomized to diet arms Attended 14 classes on intervention diet, healthy diet choices and food preparation at home. First 8 weeks, both arms advised to ""go low as you can go"" (<20g fat/d or <20g carb/d), then gradually increase fat or carb, to establish level that could be maintained long term. No E restriction. Increasing physical activity encouraged. Patient encouraged to keep daily food journal and computer tracking. Given pedometers."
Y
"See Intervention Advised to reduce carb to 20g net carbs/day Reported intake at 6 months: E: 1480kcal/d Carb: 22%E Protein: 25%E Fat: 53%E "
"Target: NS varied over time Intake: 22%"
"Target: none Intake: 53%"
"See Intervention Low-fat group: Advised to reduce fat to 20g/day Reported intake at 6 months: E: 1548kcal/d Carb: 57%E Protein 22%E Fat: 21%E "
"Primary: Weight loss mediated by insulin resistance status. Secondary: lipids, insulin, FBG, SBP, DBP, prevalence of metabolic syndrome"
"No SS main effects were detected for weight loss by diet group or IR status. SS differences in several secondary outcomes"
"WG: NR BG: N BG NSS for all comparisons"
*
0
NR
*
*
NR
*
*
"WG: NR BG: N TG increased slightly across the four groups, but no SS BG differences were found for diet or diet x insulin resistance status."
*
0
"WG: NR BG: N At 6 mo LF-IR: -14.4mg/dL LC-IR: +6.5mg/dL LF-IS: -20.8mg/dL LC-IS: +17.8mg/dL LF-IS SS more effective than LC-IS. SS p=0.006"
*
0
"WG: NR BG: N TG decreased ~25% across the four groups, but no SS BG differences were found for diet or diet x insulin resistance status. "
*
0
*
*
"WG: NR BG: N Substantial weight loss (9kg, 8.9%) was achieved overall, but no SS BG differences were found for diet or diet x insulin resistance status. Weight loss at 6 months LF-IR: -7.5 kg LC-IR: -9.6kg LF-IS: -10.4kg LC-IS: -8.6 kg"
*
0
"WG: NR BG: N Decreased NSS across the four groups, and no SS BG differences were found for diet or diet x insulin resistance status. "
*
0
"WG: NR BG: N Decreased NSS across the four groups, and no SS BG differences were found for diet or diet x insulin resistance status. "
*
0
"WG: NR BG: Y LF-IR: -8.2mU/mL LC-IR: -12.7 LF-IS: -4.5 LC-IS: -3.8 LC-IR SS more effective than LF-IS and LC-IS p=0.03"
*
1
"Area under curve insulin concentration WG: NR BG: Y LF-IR: -57.6mU min/ml LC-IR: -67.5 LF-IS: -15.1 LC-IS: -18.3 Both LF-IR and LC-IR SS more effective than LC-IS. p<0.0001. "
*
1
NR
*
*
NR
NR
Prevalence of metabolic syndrome: NSS change for diets and diet x IR status groups.
Substantial weight loss achieved but interaction between diet and insulin status not observed; the latter may be due to emphasis across groups on healthy food choices (i.e., avoidance of refined carbohydrates). May also be due to differences in methodology compared to four previous studies about the same research question, as well as small sample which affected detection of effect.
Abbreviations:
AHA - American Heart Association;
ALT - alanine aminotransferase;
AMDR - acceptable macronutrient distribution range;
AST - aspartate aminotransferase;
BG - between study groups;
BHOB - beta-hydroxybutyrate;
DBP - diastolic blood pressure;
E- energy, caloric intake;
eGFR - estimated glomerular filtration rate;
FBG - fasting blood glucose;
GGT - gamma-glutamyl transferase;
HDL-C - high-density lipoprotein cholesterol;
iGFR - isotope glomerurar filtration rate;
LDL-C - low-density lipoprotein cholesterol;
NAFLD - non-alcoholic fatty liver disease;
NR - not reported (or data needed for calculation not available);
N - no;
NA - not applicable;
NS - not specified;
NSS - not statistically significant;
SBP - systolic blood pressure;
SS - statistically significant;
TG - triglyceride;
total C - total cholesterol;
V - varied, mixed;
WG - within a study group;
WMD - weighted mean difference;
Y - yes
Number of People in Studies:
3,296 Enrolled in randomized controlled trials on 25% or less carbohydrates
2,626 Completed randomized controlled trials on 25% or less carbohydrates
79.67% 82% completion of studies
Duration of Trial
<6 Months
6-9 Months
1 -2 years
>2 years
# of Trials
36
6
9s
1