Healthy obesity

Associations of testosterone and sex hormone binding globulin with adipose tissue hormones in midlife women

OBJECTIVE

Regulators of adipose tissue hormones remain incompletely understood, but may include sex hormones. As adipose tissue hormones have been shown to contribute to numerous metabolic and cardiovascular disorders, understanding their regulation in midlife women is of clinical importance. Therefore, we assessed the associations between testosterone (T) and sex hormone binding globulin (SHBG) with leptin, high molecular weight (HMW) adiponectin, and the soluble form of the leptin receptor (sOB-R) in healthy midlife women.

DESIGN AND METHODS

Cross-sectional analyses were performed using data from 1,881 midlife women (average age 52.6 (±2.7) years) attending the sixth Annual follow-up visit of the multiethnic Study of Women's Health Across the Nation.

RESULTS

T was weakly negatively associated with both HMW adiponectin and sOB-R (r = -0.12 and r = -0.10, respectively; P < 0.001 for both), and positively associated with leptin (r = 0.17; P < 0.001). SHBG was more strongly and positively associated with both HMW adiponectin and sOB-R (r = 0.29 and r = 0.24, respectively; P < 0.001 for both), and more strongly and negatively associated with leptin (r = -0.27; P < 0.001). Adjustment for fat mass, insulin resistance, or waist circumference only partially diminished associations with HMW adiponectin and sOB-R, but attenuated associations with leptin. In conclusion, in these midlife women, lower SHBG values, and to a lesser extent, higher T levels, were associated with lower, or less favorable, levels of adiponectin and sOB-R, independent of fat mass.

CONCLUSIONS

These data suggest that variation in these adipose hormones resulting from lower SHBG levels, and possibly, though less likely, greater androgenicity, may contribute to susceptibility for metabolic and cardiovascular outcomes during midlife in women.

Altered expression of genes involved in lipid metabolism in obese subjects with unfavourable phenotype

Obesity (BMI ≥30 kg/m(2)) increases the risk of developing lifestyle-related diseases. A subgroup of obese individuals has been described as "metabolically healthy, but obese" (MHO). In contrast to at-risk obese (ARO), the MHO phenotype is defined by a favourable lipid profile and a normal or only slightly affected insulin sensitivity, despite the same amount of body fat. The objective was to characterize the metabolic phenotype of MHO subjects. We screened a variety of genes involved in lipid metabolism and inflammation in peripheral blood mononuclear cells (PBMC). Obese subjects (men and women; 18-70 years) with BMI ≥30 kg/m(2) were characterized as MHO (n = 9) or as ARO (n = 10). In addition, eleven healthy, normal weight subjects characterized as healthy by the same criteria as described for the MHO subjects were included. We found that with similar weight, total fat mass and fat mass distribution, the ARO subjects have increased plasma levels of gamma-glutamyl transpeptidase and free fatty acids. This group also has altered expression levels of a number of genes linked to lipid metabolism in PBMC with reduced gene expression levels of uncoupling protein 2, hormone-sensitive lipase and peroxisome proliferator-activated receptor δ compared with MHO subjects. The present metabolic differences between subgroups of obese subjects may contribute to explain some of the underlying mechanisms causing the increased risk of disease among ARO subjects compared with MHO subjects.

Metabolic syndrome in healthy obese, overweight, and normal weight individuals: the Atherosclerosis Risk in Communities Study

OBJECTIVE

There is recent interest in characterizing the subset of obese (OB) individuals who have healthy metabolic profiles yet only two studies have examined this group prospectively but not in racially diverse populations.

DESIGN AND METHODS

We analyzed factors associated with the prevalence and incidence of metabolic syndrome (MetSyn) among individuals grouped by BMI categories in a multi-center, community-based cohort of 14,663 African-American and white men and women aged 45-64 years at recruitment in 1987-1989, the Atherosclerosis Risk in Communities (ARIC) Study. Logistic and proportional hazards regression were utilized to estimate odds ratios (ORs) for the prevalence and hazard ratios (HRs) for incidence of MetSyn with 95% confidence intervals (CIs).

RESULTS

At visit 1, MetSyn was positively associated with age, female gender, African-American race, and inversely related to education, associations being more pronounced among normal weight (NW) subjects. Among those without MetSyn at visit 1, OB subjects were more likely to develop MetSyn compared with NW (HR (95% CI): 4.53 (4.09-5.01)). Several factors were associated with incident MetSyn among NW, including older age (per year: 1.05 (1.03-1.06)), female gender (vs. male: 1.29 (1.10-1.52)), heavy alcohol intake (vs. never: 0.75 (0.59-0.94)), and physical activity (tertile 3 vs. tertile 1: 0.71 (0.58-0.86)) but not OB. Weight gain (>5%) was also more highly associated with MetSyn in NW (1.61 (1.28-2.02)) compared with OB (1.01 (0.85-1.20)).

CONCLUSIONS

We conclude that lifestyle factors may play a stronger role in the development of MetSyn in NW individuals compared with OB and that metabolically healthy obesity may not be a stable condition.

Contribution of 24 obesity-associated genetic variants to insulin resistance, pancreatic beta-cell function and type 2 diabetes risk in the French population

CONTEXT

Obesity is the major determinant of type 2 diabetes (T2D), presumably through its effect on insulin resistance. Genome-wide association studies reported many single-nucleotide polymorphisms (SNPs) that increase obesity risk and body mass index (BMI), but their impact on T2D-related traits and risk is unclear.

OBJECTIVE

We aimed at analyzing the effect of 24 obesity risk alleles, separately and in combination, on variation of both insulin resistance and β-cell dysfunction, and on T2D risk.

DESIGN

We genotyped 24 obesity-associated SNPs and calculated an obesity genotype score (sum of the obesity risk alleles per individual). We analyzed the contribution of each SNP and this score to the variation of four metabolic indices: homeostasis model assessment of insulin resistance (HOMA-IR), homeostasis model assessment of the pancreatic β-cell function (HOMA-B), insulin sensitivity index (ISI) and insulinogenic index (II) (in up to 8050 nondiabetic French individuals) and to T2D risk (in 2077 T2D cases and 3085 controls).

RESULTS

We found a highly significant effect of the obesity genotype score on increased insulin resistance adjusted for age and gender (β=0.02; P-value=7.16 × 10(-9) for HOMA-IR). Individually, we identified nominal or significant association between increased insulin resistance and risk alleles in FAIM2, FTO, GNPDA2, MC4R, NPC1, PTER and SH2B1. Most signals, including the obesity genotype score and FTO SNP, were also associated with increased β-cell function (β=0.01; P-value=1.05 × 10(-6) and β=0.04; P-value=3.45 × 10(-4), respectively). In our T2D case-control study, only the obesity genotype score and the well-known FTO locus significantly contributed to T2D risk (OR=1.03; P-value=9.99 × 10(-3) and OR=1.15; P-value=9.46 × 10(-4), respectively). Adjustment for BMI abolished all significant associations.

CONCLUSIONS

Genetic predisposition to obesity contributes to increased insulin resistance and to its compensation through increased β-cell function, and weakly increases the T2D risk. These associations are mediated by BMI.

Effects of weight loss and insulin reduction on arterial stiffness in the SAVE trial

Background

Chronic arterial stiffness contributes to the negative health effects of obesity and insulin resistance, which include hypertension, stroke, and increased cardiovascular and all-cause mortality. Weight loss and improved insulin sensitivity are individually associated with improved central arterial stiffness; however, their combined effects on arterial stiffness are poorly understood. The purpose of this study was to determine how insulin levels modify the improvements in arterial stiffness seen with weight loss in overweight and obese young adults.

Methods

To assess the effects of weight loss and decreased fasting insulin on vascular stiffness, we studied 339 participants in the Slow the Adverse Effects of Vascular Aging (SAVE) trial. At study entry, the participants were aged 20–45, normotensive, non-diabetic, and had a body-mass index of 25–39.9 kg/m². Measures of pulse wave velocity (PWV) in the central (carotid-femoral (cfPWV)), peripheral (femoral-ankle (faPWV)), and mixed (brachial-ankle (baPWV)) vascular beds were collected at baseline and 6 months. The effects of 6-month change in weight and insulin on measures of PWV were estimated using multivariate regression.

Results

After adjustment for baseline risk factors and change in systolic blood pressure, 6-month weight loss and 6-month change in fasting insulin independently predicted improvement in baPWV but not faPWV or cfPWV. There was a significant interaction between 6-month weight change and change in fasting insulin when predicting changes in baPWV (p < 0.001). Individuals experiencing both weight loss and insulin reductions showed the greatest improvement in baPWV.

Conclusions

Young adults with excess weight who both lower their insulin levels and lose weight see the greatest improvement in vascular stiffness. This improvement in vascular stiffness with weight loss and insulin declines may occur throughout the vasculature and may not be limited to individual vascular beds.

Trial registration

NCT00366990

Exercise in the metabolic syndrome

The metabolic syndrome is a clustering of obesity, diabetes, hyperlipidemia, and hypertension that is occurring in increasing frequency across the global population. Although there is some controversy about its diagnostic criteria, oxidative stress, which is defined as imbalance between the production and inactivation of reactive oxygen species, has a major pathophysiological role in all the components of this disease. Oxidative stress and consequent inflammation induce insulin resistance, which likely links the various components of this disease. We briefly review the role of oxidative stress as a major component of the metabolic syndrome and then discuss the impact of exercise on these pathophysiological pathways. Included in this paper is the effect of exercise in reducing fat-induced inflammation, blood pressure, and improving muscular metabolism.

Excess body fat in obese and normal-weight subjects

Excess body adiposity, especially abdominal obesity and ectopic fat accumulation, are key risk factors in the development of a number of chronic diseases. The advent of in vivo imaging methodologies that allow direct assessment of total body fat and its distribution have been pivotal in this process. They have helped to identify a number of sub-phenotypes in the general population whose metabolic risk factors are not commensurate with their BMI. At least two such sub-phenotypes have been identified: subjects with normal BMI, but excess intra-abdominal (visceral) fat (with or without increased ectopic fat) and subjects with elevated BMI (> 25 kg/m(2)) but low visceral and ectopic fat. The former sub-phenotype is associated with adverse metabolic profiles, while the latter is associated with a metabolically normal phenotype, despite a high BMI. Here, examples of these phenotypes are presented and the value of carrying out enhanced phenotypical characterisation of subjects in interventional studies discussed.

Toward a unifying hypothesis of metabolic syndrome

Despite a lack of consistent diagnostic criteria, the metabolic syndrome (MetS) is increasingly evident in children and adolescents, portending a tsunami of chronic disease and mortality as this generation ages. The diagnostic criteria for MetS apply absolute cutoffs to continuous variables and fail to take into account aging, pubertal changes, and race/ethnicity. We attempt to define MetS mechanistically to determine its specific etiologies and to identify targets for therapy. Whereas the majority of studies document a relationship of visceral fat to insulin resistance, ectopic liver fat correlates better with dysfunctional insulin dynamics from which the rest of MetS derives. In contrast to the systemic metabolism of glucose, the liver is the primary metabolic clearinghouse for 4 specific foodstuffs that have been associated with the development of MetS: trans-fats, branched-chain amino acids, ethanol, and fructose. These 4 substrates (1) are not insulin regulated and (2) deliver metabolic intermediates to hepatic mitochondria without an appropriate "pop-off" mechanism for excess substrate, enhancing lipogenesis and ectopic adipose storage. Excessive fatty acid derivatives interfere with hepatic insulin signal transduction. Reactive oxygen species accumulate, which cannot be quenched by adjacent peroxisomes; these reactive oxygen species reach the endoplasmic reticulum, leading to a compensatory process termed the "unfolded protein response," driving further insulin resistance and eventually insulin deficiency. No obvious drug target exists in this pathway; thus, the only rational therapeutic approaches remain (1) altering hepatic substrate availability (dietary modification), (2) reducing hepatic substrate flux (high fiber), or (3) increasing mitochondrial efficiency (exercise).

Incident cardiovascular disease events in metabolically benign obese individuals

Nearly one-third of obese individuals are classified as metabolically benign; however whether this subgroup is at a lower risk of cardiovascular disease (CVD) is unclear. Using pooled data from the Atherosclerosis Risk in Communities and Cardiovascular Health Studies, we assessed incident CVD (coronary heart disease and stroke) using three definitions of the metabolically benign phenotype: (i) the ATP-III metabolic syndrome definition (≤2 of the ATP-III components, excluding abdominal obesity (ii) the expanded ATP-III definition (≤1 of: any ATP-III components, insulin resistance (IR), or systemic inflammation), and (iii) the IR-based definition (sex-specific lowest quartile of the HOMA(IR) distribution). The sample included 6,106 normal weight, 7,115 overweight, and 4,323 obese participants. Among obese, 27.0%, 18.1%, and 20.4% were metabolically benign by the three definitions, respectively. The CVD incidence rates (mean follow-up 11.8 years) were 7.1, 5.8, and 8.4 per 1,000 person-years in metabolically benign obese via the three definitions, respectively, compared to 14.3, 13.8, and 13.3 in at-risk obese, and 7.5, 6.7, and 8.2 in metabolically benign normal weight participants. Multivariable-adjusted hazard ratios of incident CVD in metabolically benign obese compared to their at-risk obese counterparts were 0.59 (95% CI 0.47-0.73), 0.52 (0.39-0.68), and 0.71 (0.57-0.90), respectively; and 1.24 (0.99-1.57), 1.16 (0.86-1.56), and 1.28 (1.01-1.62) compared to metabolically benign normal weight individuals. Only 28.7% of obese participants classified as metabolically benign by at least one definition were "metabolically benign" by all three definitions. Despite similar CVD risk estimates, the three definitions identified different subgroups of the obese population, perhaps suggesting distinct etiologies.

Impact of metabolic comorbidity on the association between body mass index and health-related quality of life: a Scotland-wide cross-sectional study of 5,608 participants

Background

The prevalence of obesity is rising in Scotland and globally. Overall, obesity is associated with increased morbidity, mortality and reduced health-related quality of life. Studies suggest that "healthy obesity" (obesity without metabolic comorbidity) may not be associated with morbidity or mortality. Its impact on health-related quality of life is unknown.

Methods

We extracted data from the Scottish Health Survey on self-reported health-related quality of life, body mass index (BMI), demographic information and comorbidity. SF-12 responses were converted into an overall health utility score. Linear regression analyses were used to explore the association between BMI and health utility, stratified by the presence or absence of metabolic comorbidity (diabetes, hypertension, hypercholesterolemia or cardiovascular disease), and adjusted for potential confounders (age, sex and deprivation quintile).

Results

Of the 5,608 individuals, 3,744 (66.8%) were either overweight or obese and 921 (16.4%) had metabolic comorbidity. There was an inverted U-shaped relationship whereby health utility was highest among overweight individuals and fell with increasing BMI. There was a significant interaction with metabolic comorbidity (p = 0.007). Individuals with metabolic comorbidty had lower utility scores and a steeper decline in utility with increasing BMI (morbidly obese, adjusted coefficient: -0.064, 95% CI -0.115, -0.012, p = 0.015 for metabolic comorbidity versus -0.042, 95% CI -0.067, -0.018, p = 0.001 for no metabolic comorbidity).

Conclusions

The adverse impact of obesity on health-related quality of life is greater among individuals with metabolic comorbidity. However, increased BMI is associated with reduced health-related quality of life even in the absence of metabolic comorbidity, casting doubt on the notion of "healthy obesity".

Hypocaloric diet and regular moderate aerobic exercise is an effective strategy to reduce anthropometric parameters and oxidative stress in obese patients

BACKGROUND

Studies show that diet and exercise are important in the treatment of obesity. The aim of this study was to determine whether additional regular moderate aerobic exercise during a treatment with hypocaloric diet has a beneficial effect on oxidative stress and molecular damage in the obese patient.

METHODS

Oxidative stress of 16 normal-weight (NW) and 32 obese 1 (O1) subjects (BMI 30-34.9 kg/m(2)) were established by biomarkers of oxidative stress in plasma. Recombinant human insulin was incubated with blood from NW or O1 subjects, and the molecular damage to the hormone was analyzed. Two groups of treatment, hypocaloric diet (HD) and hypocaloric diet plus regular moderate aerobic exercise (HDMAE), were formed, and their effects in obese subjects were analyzed.

RESULTS

The data showed the presence of oxidative stress in O1 subjects. Molecular damage and polymerization of insulin was observed more frequently in the blood from O1 subjects. The treatment of O1 subjects with HD decreased the anthropometric parameters as well as oxidative stress and molecular damage, which was more effectively prevented by the treatment with HDMAE.

CONCLUSION

HD and HDMAE treatments decreased anthropometric parameters, oxidative stress, and molecular damage in O1 subjects.

Genetic polymorphisms in carnitine palmitoyltransferase 1A gene are associated with variation in body composition and fasting lipid traits in Yup'ik Eskimos

Variants of carnitine palmitoyltransferase 1A (CPT1A), a key hepatic lipid oxidation enzyme, may influence how fatty acid oxidation contributes to obesity and metabolic outcomes. CPT1A is regulated by diet, suggesting interactions between gene variants and diet may influence outcomes. The objective of this study was to test the association of CPT1A variants with body composition and lipids, mediated by consumption of polyunsaturated fatty acids (PUFA). Obesity phenotypes and fasting lipids were measured in a cross-sectional sample of Yup'ik Eskimo individuals (n = 1141) from the Center of Alaska Native Health Research (CANHR) study. Twenty-eight tagging CPT1A SNPs were evaluated with outcomes of interest in regression models accounting for family structure. Several CPT1A polymorphisms were associated with HDL-cholesterol and obesity phenotypes. The P479L (rs80356779) variant was associated with all obesity-related traits and fasting HDL-cholesterol. Interestingly, the association of P479L with HDL-cholesterol was still significant after correcting for body mass index (BMI), percentage body fat (PBF), or waist circumference (WC). Our findings are consistent with the hypothesis that the L479 allele of the CPT1A P479L variant confers a selective advantage that is both cardioprotective (through increased HDL-cholesterol) and associated with reduced adiposity.

High leptin/adiponectin ratio and serum triglycerides are associated with an "at-risk" phenotype in young severely obese patients

"At-risk" severely obese subjects are characterized by insulin resistance, and higher visceral fat and plasma lipid levels compared with metabolically healthy obese (MHO) subjects, although both groups have a high BMI and fat mass. The aim of this study was to measure several serum adipokines and gastrointestinal hormones in a young severely obese population from Southern Italy to identify biochemical markers of the "at-risk" insulin-resistant obese profile. We studied 160 unrelated white young adults (mean age = 25.2 years, mean BMI = 44.9 kg/m(2), 65% women) affected by obesity for at least 5 years. Serum concentrations of glucagon, ghrelin, gastric inhibitory peptide, glucagon like peptide-1, interleukin-6, tumor necrosis factor α, leptin, adiponectin, adipsin, and visfatin were measured. The leptin/adiponectin (L/A) ratio and fatty liver index (FLI) were calculated. We found a prevalence of 21.3% of MHO patients in our young severely obese patients. At univariate analysis, the "at-risk" group had higher mean levels of BMI (P < 0.0001), leptin (P = 0.039, men) and the L/A ratio (P = 0.003), and lower mean levels of visfatin (P = 0.026) than the MHO group. The L/A ratio, serum triglycerides, and male sex were significantly associated with "at-risk" obesity and accounted for 19.5% of insulin resistance at multivariate analysis. In conclusion, we demonstrate that a high serum L/A ratio and high levels of serum triglycerides may be markers of "at-risk" obesity, independent of waist circumference (WC) and BMI, in young severely obese population.

Melanin and melanogenesis in adipose tissue: possible mechanisms for abating oxidative stress and inflammation?

Obesity has become a worldwide epidemic and can lead to multiple chronic diseases. Adipose tissue is increasingly thought to play an active role in obesity-related pathologies such as insulin resistance and non-alcoholic fatty liver disease. Obesity has been strongly associated with systemic inflammation and, to a lesser degree, with oxidative stress, although the causal relationships among these factors are unclear. A recent study demonstrating an expression of the components of the melanogenic pathway and the presence of melanin in visceral adipose has raised questions regarding the possible role of melanogenesis in adipose tissue. As this study also found larger amounts of melanin in the adipose tissue of obese patients relative to lean ones, we hypothesize that melanin, a pigment known for its antioxidant and anti-inflammatory properties, may scavenge reactive oxygen species and abate oxidative stress and inflammation in adipose tissue. This review considers the evidence to support such a hypothesis, and speculates on the role of melanin within adipocytes. Furthermore, we consider whether the α-melanocyte-stimulating hormone or its synthetic analogues could be used to stimulate melanin production in adipocytes, should the hypothesis be supported in future experiments.

Genetic predisposition to obesity leads to increased risk of type 2 diabetes

AIMS/HYPOTHESIS

Obesity is a major risk factor for type 2 diabetes. Recent genome-wide association (GWA) studies have identified multiple loci robustly associated with BMI and risk of obesity. However, information on their associations with type 2 diabetes is limited. Such information could help increase our understanding of the link between obesity and type 2 diabetes. We examined the associations of 12 obesity susceptibility loci, individually and in combination, with risk of type 2 diabetes in the population-based European Prospective Investigation of Cancer (EPIC) Norfolk cohort.

METHODS

We genotyped 12 SNPs, identified by GWA studies of BMI, in 20,428 individuals (aged 39-79 years at baseline) with an average follow-up of 12.9 years, during which 729 individuals developed type 2 diabetes. A genetic predisposition score was calculated by adding the BMI-increasing alleles across the 12 SNPs. Associations with incidence of type 2 diabetes were examined by logistic regression models.

RESULTS

Of the 12 SNPs, eight showed a trend with increased risk of type 2 diabetes, consistent with their BMI-increasing effects. Each additional BMI-increasing allele in the genetic predisposition score was associated with a 4% increased odds of developing type 2 diabetes (OR 1.041, 95% CI 1.005-1.078; p = 0.02). Adjustment for BMI completely abolished the association with incident type 2 diabetes (OR 1.003, 95% CI 0.967-1.039; p = 0.89).

CONCLUSIONS/INTERPRETATION

The genetic predisposition to obesity leads to increased risk of developing type 2 diabetes, which is completely mediated by its obesity-predisposing effect.

Metabolically healthy obese women and functional capacity

BACKGROUND

Obesity and the metabolic syndrome are significant determinants of functional capacity in women. In the past decade, the term "metabolically healthy obese" (MHO) emerged in the literature to identify a distinct category of obese individuals presenting less metabolic impairment than expected. However, MHO women might have similar risk than non-MHO women for nonmetabolic weight-related co-morbidities, including altered functional capacity.

METHODS

Eighty six obese women aged from 28 to 74 years old were studied. MHO was defined as a body mass index (BMI) ≥30.0 kg/m(2) with less than one metabolic syndrome criteria based on the Adult Treatment Panel III (ATP III) definition. Walking distance (m) and walking speed (m/sec), evaluated by the 6-min walk test, were used as indicators of functional capacity.

RESULTS

Twenty one percent of the sample was considered MHO. Age, BMI, physical activity level, and diastolic blood pressure were not significantly different between MHO and non-MHO women. MHO women performed better on the 6-min walk test (519.8 m±68.2 vs. 448.4 m±67.1; P≤0.01) compared to non-MHO women. Moreover, in multiple regression analyses, MHO status and BMI were significantly associated with walking speed after adjustment for age, physical activity level, the total number of chronic conditions, and arthritis/osteoarthritis.

CONCLUSIONS

Our results show that MHO women have a better functional capacity than non-MHO women, and therefore could be at lower risk for future disability. However, weight management remains important because BMI was also an independent predictor of functional capacity regardless of metabolic profile.

Chronic inflammation in obesity and the metabolic syndrome

The increasing incidence of obesity and the metabolic syndrome is disturbing. The activation of inflammatory pathways, used normally as host defence, reminds the seriousness of this condition. There is probably more than one cause for activation of inflammation. Apparently, metabolic overload evokes stress reactions, such as oxidative, inflammatory, organelle and cell hypertrophy, generating vicious cycles. Adipocyte hypertrophy, through physical reasons, facilitates cell rupture, what will evoke an inflammatory reaction. Inability of adipose tissue development to engulf incoming fat leads to deposition in other organs, mainly in the liver, with consequences on insulin resistance. The oxidative stress which accompanies feeding, particularly when there is excessive ingestion of fat and/or other macronutrients without concomitant ingestion of antioxidant-rich foods/beverages, may contribute to inflammation attributed to obesity. Moreover, data on the interaction of microbiota with food and obesity brought new hypothesis for the obesity/fat diet relationship with inflammation. Beyond these, other phenomena, for instance psychological and/or circadian rhythm disturbances, may likewise contribute to oxidative/inflammatory status. The difficulty in the management of obesity/metabolic syndrome is linked to their multifactorial nature where environmental, genetic and psychosocial factors interact through complex networks.

Fructose and metabolic diseases: new findings, new questions

There has been much concern regarding the role of dietary fructose in the development of metabolic diseases. This concern arises from the continuous increase in fructose (and total added caloric sweeteners consumption) in recent decades, and from the increased use of high-fructose corn syrup (HFCS) as a sweetener. A large body of evidence shows that a high-fructose diet leads to the development of obesity, diabetes, and dyslipidemia in rodents. In humans, fructose has long been known to increase plasma triglyceride concentrations. In addition, when ingested in large amounts as part of a hypercaloric diet, it can cause hepatic insulin resistance, increased total and visceral fat mass, and accumulation of ectopic fat in the liver and skeletal muscle. These early effects may be instrumental in causing, in the long run, the development of the metabolic syndrome. There is however only limited evidence that fructose per se, when consumed in moderate amounts, has deleterious effects. Several effects of a high-fructose diet in humans can be observed with high-fat or high-glucose diets as well, suggesting that an excess caloric intake may be the main factor involved in the development of the metabolic syndrome. The major source of fructose in our diet is with sweetened beverages (and with other products in which caloric sweeteners have been added). The progressive replacement of sucrose by HFCS is however unlikely to be directly involved in the epidemy of metabolic disease, because HFCS appears to have basically the same metabolic effects as sucrose. Consumption of sweetened beverages is however clearly associated with excess calorie intake, and an increased risk of diabetes and cardiovascular diseases through an increase in body weight. This has led to the recommendation to limit the daily intake of sugar calories.