Long-term effects of a high-protein, low-carbohydrate diet on weight control and cardiovascular risk markers in obese hyperinsulinemic subjects

Abstract

OBJECTIVE:To compare the long-term compliance and effects of two low-fat diets differing in carbohydrate to protein ratio on body composition and biomarkers of cardiovascular disease risk in obese subjects with hyperinsulinemia. DESIGN: Outpatient, parallel, clinical intervention study of two groups of subjects randomly assigned to either a standard protein (SP; 15% protein, 55% carbohydrate) or high-protein (HP; 30% protein, 40% carbohydrate) diet, during 12 weeks of energy restriction (B6.5 MJ/day) and 4 weeks of energy balance (B8.3 MJ/day). Subsequently, subjects were asked to maintain the same dietary pattern for the succeeding 52 weeks with minimal professional support. SUBJECTS: A total of 58 obese, nondietetic subjects with hyperinsulinemia (13 males/45 females, mean age 50.2 y, mean body mass index (BMI) 34.0 kg/m 2 , mean fasting insulin 17.8 mU/l) participated in the study. MEASUREMENTS: Body composition, blood pressure, blood lipids, fasting glucose, insulin, CRP and sICAM-1 were measured at baseline and at weeks 16 and 68. Urinary urea/creatinine ratio was measured at baseline, week 16 and at 3 monthly intervals thereafter. RESULTS: In total, 43 subjects completed the study with similar dropouts in each group (P ¼ 0.76). At week 68, there was net weight loss (SP À2.973.6%, HP À4.175.8%; Po0.01) due entirely to fat loss (Po0.001) with no diet effect. Both diets significantly increased HDL cholesterol concentrations (Po0.001) and decreased fasting insulin, insulin resistance, sICAM-1 and CRP levels (Po0.05). Protein intake was significantly greater in HP during the initial 16 weeks (Po0.001), but decreased in HP and increased in SP during 52-week follow-up, with no difference between groups at week 68, indicating poor long-term dietary adherence behaviour to both dietary patterns. CONCLUSION: Without active ongoing dietary advice, adherence to dietary intervention is poor. Nonetheless, both dietary patterns achieved net weight loss and improvements in cardiovascular risk factors.

Long-term effects of popular dietary approaches on weight loss and features of insulin resistance

“…The approach used was intended to reproduce what might occur in clinical practice with intensive dietary advice and monitoring provided for the first few months, and participants unsupervised during the following 8-month period. A major strength of this study was the high retention rate compared with other similar studies, 6,17,19,20 enabling statistical analysis to be undertaken on an intention to treat basis. Of interest was the remarkably high rate of retention among those in the HP group.…”

“…One might have expected the substantial improvements noted during the first 6 months to be maintained. However, the HP group reported intakes of total and saturated fatty acids that were far greater than prescribed and incompatible 19,20 one in people with type 2 diabetes, the other in obese normoglycaemic individuals, compared HP and conventional diets. They reported no difference between the two diets, but attrition rates were very high.…”

“…Zone) 5 diets, which have been shown in many studies of free-living individuals to be associated with impressive weight loss and improved cardiovascular risk indicators over a relatively short period of time (up to 6 months). [6][7][8][9][10][11][12][13][14][15][16] Very few data are available relating to longterm (12 months or greater) comparisons of such alternative dietary regimens 6,[17][18][19][20] and only one study has been published that compares HP, HF and the more widely recommended HC-high-fibre diet over a prolonged period. 21 We have previously reported a 6-month comparison of such diets in overweight insulin-resistant women.…”

CRP reduction following gastric bypass surgery is most pronounced in insulin-sensitive subjects

“…3,10,19,[36][37][38] A study of healthy premenopausal women who completed a 1-y weight loss programme achieved a minimum 10% loss of weight and a decrease in cytokine (IL-6 and TNF-a) produc- CRP reduction following gastric bypass surgery C Holdstock et al tion. 34 Medical treatment with sibutramine or orlistat for 6 months achieved a reduction in CRP despite less weight loss (2-5.4%).…”

An immune origin of type 2 diabetes?

“…Here, again, polymorphisms in immune genes modulate risk, implying a pathogenetic significance for immune gene products Table 4 Interventions that have an impact on the inflammatory state Inflammatory mediators whose concentrations are reduced by weight loss and/or physical exercise [190][191][192][193][194][195][196][197][198][199][200][201][202][203][204][205][206][207] CRP, TNF-α, soluble TNF-α receptor 2, IL-6, IL-18, MCP-1, PAI-1, t-PA, soluble ICAM-1, soluble VCAM-1, P-selectin Inflammatory mediators whose concentrations are reduced by glucose-lowering drugs [186,188,[208][209][210][211][212][213][214][215][216][217] Sulphonylurea: TNF-α Metformin: CRP Glitazones: CRP, SAA, TNF-α, soluble CD40 ligand, PAI-1 Insulin: CRP, IL-1, IL-6, TNF-α, soluble ICAM-1, MCP-1, PAI-1 SAA Serum amyloid A, t-PA tissue plasminogen activator, VCAM-1 vascular cell adhesion molecule-1 [171][172][173]. Where studied, the upregulation of inflammatory mediators was linked to increased oxidative stress, impaired mitochondrial function and abnormal cholesterol metabolism [174][175][176].…”