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BACKGROUND/OBJECTIVES: Our objective was to investigate changes in liver fat and insulin sensitivity during a 2-year diet intervention. An ad libitum Paleolithic diet (PD) was compared with a conventional low-fat diet (LFD).

SUBJECTS/METHODS: Seventy healthy, obese, postmenopausal women were randomized to either a PD or a conventional LFD. Diet intakes were ad libitum. Liver fat was measured with proton magnetic resonance spectroscopy. Insulin sensitivity was evaluated with oral glucose tolerance tests and calculated as homeostasis model assessment-insulin resistance (HOMA-IR)/liver insulin resistance (Liver IR) index for hepatic insulin sensitivity and oral glucose insulin sensitivity (OGIS)/Matsuda for peripheral insulin sensitivity. All measurements were performed at 0, 6 and 24 months. Forty-one women completed the examinations for liver fat and were included.

RESULTS: Liver fat decreased after 6 months by 64% (95% confidence interval: 54-74%) in the PD group and by 43% (27-59%) in the LFD group (P<0.01 for difference between groups). After 24 months, liver fat decreased 50% (25-75%) in the PD group and 49% (27-71%) in the LFD group. Weight reduction between baseline and 6 months was correlated to liver fat improvement in the LFD group (rs=0.66, P<0.01) but not in the PD group (rs=0.07, P=0.75). Hepatic insulin sensitivity improved during the first 6 months in the PD group (P<0.001 for Liver IR index and HOMA-IR), but deteriorated between 6 and 24 months without association with liver fat changes.

CONCLUSIONS: A PD with ad libitum intake had a significant and persistent effect on liver fat and differed significantly from a conventional LFD at 6 months. This difference may be due to food quality, for example, a higher content of mono- and polyunsaturated fatty acids in the PD. Changes in liver fat did not associate with alterations in insulin sensitivity.International Journal of Obesity advance online publication, 16 February 2016; doi:10.1038/ijo.2016.4.

Background

Means to reduce future risk for cardiovascular disease in subjects with type 2 diabetes are urgently needed.

Methods

Thirty-two patients with type 2 diabetes (age 59 ± 8 years) followed a Paleolithic diet for 12 weeks. Participants were randomized to either standard care exercise recommendations (PD) or 1-h supervised exercise sessions (aerobic exercise and resistance training) three times per week (PD-EX).

Results

For the within group analyses, fat mass decreased by 5.7 kg (IQR: −6.6, −4.1; p < 0.001) in the PD group and by 6.7 kg (−8.2, −5.3; p < 0.001) in the PD-EX group. Insulin sensitivity (HOMA-IR) improved by 45% in the PD (p < 0.001) and PD-EX (p < 0.001) groups. HbA_1c decreased by 0.9% (−1.2, −0.6; p < 0.001) in the PD group and 1.1% (−1.7, −0.7; p < 0.01) in the PD-EX group. Leptin decreased by 62% (p < 0.001) in the PD group and 42% (p < 0.001) in the PD-EX group. Maximum oxygen uptake increased by 0.2 L/min (0.0, 0.3) in the PD-EX group, and remained unchanged in the PD group (p < 0.01 for the difference between intervention groups). Male participants decreased lean mass by 2.6 kg (−3.6, −1.3) in the PD group and by 1.2 kg (−1.3, 1.0) in the PD-EX group (p < 0.05 for the difference between intervention groups).

Conclusions

A Paleolithic diet improves fat mass and metabolic balance including insulin sensitivity, glycemic control, and leptin in subjects with type 2 diabetes. Supervised exercise training may not enhance the effects on these outcomes, but preserves lean mass in men and increases cardiovascular fitness.

Aims/hypothesis We aimed to identify which surrogate index of insulin sensitivity has the strongest correlation with the reference measurement, the hyperinsulinaemic-euglycaemic clamp (HEC), to determine which surrogate measure should be recommended for use in large-scale studies. Methods A literature search (1979-2012) was conducted to retrieve all articles reporting bivariate correlations between the HEC and surrogate measures of insulin sensitivity (in fasting samples or during the OGTT). We performed a random effects meta-analysis for each surrogate measure to integrate the correlation coefficients of the different studies. Results The OGTT-based surrogate measures with the strongest pooled correlations (r) to the HEC were the Stumvoll metabolic clearance rate (Stumvoll MCR; r=0.70 [95% CI 0.61, 0.77], n=5), oral glucose insulin sensitivity (OGIS; r=0.70 [0.57, 0.80], n=6), the Matsuda index (r=0.67 [0.61, 0.73], n=19), the Stumvoll insulin sensitivity index (Stumvoll ISI; r=0.67 [0.60, 0.72], n=8) and the Gutt index (r=0.65 [0.60, 0.69], n=6). The fasting surrogate indices that correlated most strongly with the HEC and had narrow 95% CIs were the revised QUICKI (r=0.68 [0.58, 0.77], n=7), the QUICKI (r=0.61 [0.55, 0.65], n=35), the log HOMA-IR (r=-0.60 [-0.66, -0.53], n=22) and the computer generated HOMA of insulin sensitivity (HOMA-%S; r=0.57 [0.46, 0.67], n=5). Conclusions/interpretation The revised QUICKI fasting surrogate measure appears to be as good as the OGTT-based Stumvoll MCR, OGIS, Matsuda, Stumvoll ISI and Gutt indices for estimating insulin sensitivity. It can therefore be recommended as the most appropriate index for use in large-scale clinical studies.