Effects of weight loss during a very low carbohydrate diet on specific adipose tissue depots and insulin sensitivity in older adults with obesity: a randomized clinical trial.

BACKGROUND: Insulin resistance and accumulation of visceral adipose tissue (VAT) and intermuscular adipose tissue (IMAT) place aging adults with obesity at high risk of cardio-metabolic disease. A very low carbohydrate diet (VLCD) may be a means of promoting fat loss from the visceral cavity and skeletal muscle, without compromising lean mass, and improve insulin sensitivity in aging adults with obesity. OBJECTIVE: To determine if a VLCD promotes a greater loss of fat (total, visceral and intermuscular), preserves lean mass, and improves insulin sensitivity compared to a standard CHO-based/low-fat diet (LFD) in older adults with obesity. DESIGN: Thirty-four men and women aged 60-75 years with obesity (body mass index [BMI] 30-40 kg/m2) were randomized to a diet prescription of either a VLCD (< 10:25:> 65% energy from CHO:protein:fat) or LFD diet (55:25:20) for 8 weeks. Body composition by dual-energy X-ray absorptiometry (DXA), fat distribution by magnetic resonance imaging (MRI), insulin sensitivity by euglycemic hyperinsulinemic clamp, and lipids by a fasting blood draw were assessed at baseline and after the intervention. RESULTS: Participants lost an average of 9.7 and 2.0% in total fat following the VLCD and LFD, respectively (p < 0.01). The VLCD group experienced ~ 3-fold greater loss in VAT compared to the LFD group (- 22.8% vs - 1.0%, p < 0.001) and a greater decrease in thigh-IMAT (- 24.4% vs - 1.0%, p < 0.01). The VLCD group also had significantly greater thigh skeletal muscle (SM) at 8 weeks following adjustment for change in total fat mass. Finally, the VLCD had greater increases in insulin sensitivity and HDL-C and decreases in fasting insulin and triglycerides compared to the LFD group. CONCLUSIONS: Weight loss resulting from consumption of a diet lower in CHO and higher in fat may be beneficial for older adults with obesity by depleting adipose tissue depots most strongly implicated in poor metabolic and functional outcomes and by improving insulin sensitivity and the lipid profile. TRIAL REGISTRATION: NCT02760641. Registered 03 May 2016 - Retrospectively registered.

Effects of a carbohydrate-restricted diet on hepatic lipid content in adolescents with non-alcoholic fatty liver disease: A pilot, randomized trial.

BACKGROUND: Non-alcoholic fatty liver disease (NAFLD) has emerged as the most common form of liver disease among adolescents in industrialized countries. While lifestyle intervention remains the hallmark treatment for NAFLD, the most effective dietary strategy to reverse NAFLD in children is unknown. OBJECTIVE: The objective of this study was to determine the effects of a moderately CHO-restricted diet (CRD) vs fat-restricted diet (FRD) in adolescents with NAFLD on reduction in liver fat and insulin resistance. METHODS: Thirty-two children/adolescents (age 9-17) with obesity and NAFLD were randomized to a CRD (<25:25:>50% energy from CHO:protein:fat) or FRD (55:25:20) for 8 weeks. Caloric intakes were calculated to be weight maintaining. Change in hepatic lipid content was measured via magnetic resonance imaging, body composition via dual energy X ray absorptiometry and insulin resistance via a fasting blood sample. RESULTS: Change in hepatic lipid did not differ with diet, but declined significantly (-6.0 ± 4.7%, P < .001 only within the CRD group. We found significantly greater decreases in insulin resistance (HOMA-IR, <.05), abdominal fat mass (P < .01) and body fat mass (P < .01) in response to the CRD vs FRD. CONCLUSION: These findings suggest that consumption of a moderately CHO-restricted diet may result in decreased hepatic lipid as well as improvements in body composition and insulin resistance in adolescents with NAFLD even in the absence of intentional caloric restriction. Larger studies are needed to determine whether a CHO-restricted diet induces change in hepatic lipid independent of change in body fat.

Effectiveness of a carbohydrate restricted diet to treat non-alcoholic fatty liver disease in adolescents with obesity: Trial design and methodology.

BACKGROUND: Non-alcoholic fatty liver disease (NAFLD) is the most common liver disorder among children in the developed world and can progress to cirrhosis, hepatocellular carcinoma, and liver failure. No evidence-based dietary guidelines exist on the most effective diet prescription to treat NAFLD. OBJECTIVE: To compare the effect of a carbohydrate (CHO)-restricted diet vs fat-restricted diet, the current standard of care, on changes in hepatic fat infiltration, body composition, and metabolic health over an 8-week period among overweight and obese children diagnosed with NAFLD. METHODS: In this two-arm, parallel design randomized controlled trial (RCT), 40 participants aged 9 to 18 years were randomized to a CHO restricted diet (<25:>50:25% daily calories from CHO: fat: protein) or control, fat restricted diet (55,20:25% daily calories from CHO: fat: protein). This family-based diet intervention included: (1) a 2-week supply of groceries to feed a four-person household specific to the assigned diet; and (2) extensive education on diet implementation through biweekly, diet-specific group and individualized counseling sessions with participants and one parent or guardian led by a registered dietitian (RD). The primary outcome measure of this study was hepatic lipid, measured using magnetic resonance spectroscopy (MRS). Secondary outcomes included liver transaminases; markers of inflammation (hsCRP, IL-6, TNF-α); body composition; visceral adipose tissue; and insulin resistance. All testing was conducted at baseline and week 8; hepatic transaminases were also measured at weeks 2 and 4. This RCT is registered with ClinicalTrials.gov (ID: NCT02787668).