The protein type within a hypocaloric diet affects obesity-related inflammation: The RESMENA project

Abstract

Objectives

The aim of this study was to compare the effect of two energy-restricted, differing with regard to protein content, on the inflammation state of obese individuals with features of metabolic syndrome.

Methods

Ninety-six participants completed an 8-wk randomized intervention trial that compared the RESMENA diet (−30% energy, with 30% energy from protein) with a control diet (−30% energy, with 15% energy from protein) that was based on American Heart Association criteria.

Results

The mean body weight losses were 7.09 ± 0.82 kg and 6.73 ± 0.71 kg, respectively, with no differences seen between the groups. The endpoint inflammation score—which was based on high-sensitivity C-reactive protein, interleukin-6, tumor necrosis factor-α, and plasminogen activator inhibitor-1 levels—was significantly lower (P = 0.012) in the low-protein group (6.81 ± 2.32 versus 7.94 ± 1.94). The linear regression analyses revealed that total protein intake was positively associated with inflammation (P = 0.007) as well as with animal protein (P = 0.025) and meat protein (P = 0.015), but neither vegetable- nor fish-derived proteins were found to influence inflammatory status.

Conclusions

Our results suggest that the type of protein consumed (more than the total protein consumed) within an energy-restricted diet influences the inflammation status associated with obesity-related comorbidities.

Introduction

Atherosclerotic cardiovascular disease is a chronic inflammatory disorder that represents a major cause of morbidity and mortality in many developed countries [1]. Metabolic syndrome (MetSyn) encompasses important cardiovascular risk factors, including central obesity, insulin resistance, hypertension, and serum lipid abnormalities [2]. Effective strategies should be encouraged to reduce the burden of cardiovascular disease, with diet being a primary tool for both prevention and the first-line treatment of such disorders [2].

Indeed, low-grade chronic inflammation has been proposed as a mechanism that links obesity and cardiovascular disturbances [3]; they are currently being redefined by including various markers that are indicative of inflammatory status, endothelial dysfunction, and obesity-related vascular damage [4]. Inflammation has already been associated with lipid profile modifications [5]. For these reasons, appropriate dietary strategies must focus on inflammatory status improvement in addition to weight and fat loss [6], [7].

Acute-phase proteins such as C-reactive protein (CRP) are relevant systemic inflammatory markers that have been shown to be upregulated in preclinical obesity as well as in advanced stages of vascular damage [8]. Some adipokines secreted by the adipose tissue (e.g., tumor necrosis factor-α [TNF-α], interleukin-6 [IL-6]) have also been assessed as useful markers of inflammation, because the adipose tissue is expanded in individuals with obesity. Furthermore, IL-6 seems to be a strong stimulator of CRP secretion with conditions of excessive fat accumulation [3]. Plasminogen activator inhibitor-I (PAI-I) levels are predictive of incident cardiovascular disease in the general population, and its secretion by adipose tissue is also increased in obese individuals and associated with increased fat mass and proinflammatory status [9]. Given the association of these markers with cardiovascular risk, it is expected that any intervention that is focused on the reduction of inflammatory status may benefit cardiovascular health.

Dietary nutrients have attracted attention in recent research as a result of their beneficial effects on cardiovascular disease via the attenuation of adverse lipid profiles, inflammation, and oxidative stress [1], [5], [10], [11]. Thus, recent nutritional investigations have considered the specific role of selected dietary components, because such components may offer additional benefits on top of weight loss [2], [12]. This has been evidenced by the DiOGenes trial [13] and the Sysdimet study [10], which demonstrated the positive effects of such things as the glycemic index, omega-3 fatty acids, whole-grain products, and bilberries. In addition, specific dietary patterns that are based on reducing total and saturated fat, cholesterol, and sugar (e.g., Dietary Approaches to Stop Hypertension [DASH], the American Heart Association [AHA] dietary pattern) have widely been proven to be protective against cardiovascular disease [14], [15].

An increase in protein content has been frequently assessed for weight-lowering strategies due to its resulting increased levels of satiety and its higher thermogenic effect [16]. Nevertheless, the role of protein intake on obesity-related inflammation and type of protein have demonstrated controversial results [17], [18], [19].

The current study evaluates the effects of two dietary strategies with different protein contents on decreasing inflammation among an obese population with features of MetSyn via the RESMENA (MEtabolic Syndrome REduction in NAvarra) project.