AFestschriftfor Roland L. Weinsier: Nutrition Scientist, Educator, and Clinician1

The pathophysiology of hypertension in patients with obesity

The combination of obesity and hypertension is associated with high morbidity and mortality because it leads to cardiovascular and kidney disease. Potential mechanisms linking obesity to hypertension include dietary factors, metabolic, endothelial and vascular dysfunction, neuroendocrine imbalances, sodium retention, glomerular hyperfiltration, proteinuria, and maladaptive immune and inflammatory responses. Visceral adipose tissue also becomes resistant to insulin and leptin and is the site of altered secretion of molecules and hormones such as adiponectin, leptin, resistin, TNF and IL-6, which exacerbate obesity-associated cardiovascular disease. Accumulating evidence also suggests that the gut microbiome is important for modulating these mechanisms. Uric acid and altered incretin or dipeptidyl peptidase 4 activity further contribute to the development of hypertension in obesity. The pathophysiology of obesity-related hypertension is especially relevant to premenopausal women with obesity and type 2 diabetes mellitus who are at high risk of developing arterial stiffness and endothelial dysfunction. In this Review we discuss the relationship between obesity and hypertension with special emphasis on potential mechanisms and therapeutic targeting that might be used in a clinical setting.

Resting energy expenditure: a stronger marker than body weight for bone mineral density in white women but not men? The Rancho Bernardo study

OBJECTIVE

To investigate the association between resting energy expenditure (REE) and bone mineral density (BMD) in white adults.

DESIGN

Cross-sectional study.

SETTING

White, middle-class to upper middle-class community-dwelling adults.

PARTICIPANTS

Women (n = 996) and men (n = 686) aged 36 to 97 years.

ASSESSMENT OF RISK FACTORS

REE calculated using the Harris-Benedict equation.

MAIN OUTCOME MEASURES

BMD of the lumbar spine (L1 to L4), total hip, and total body measured using dual energy x-ray absorptiometry.

RESULTS

REE was lower in women than in men (1220 versus 1566 kcal/day, P < 0.0001); women also had lower BMI. After adjusting for lean body mass (LBM), REE was higher in women than men (1407 versus 1296 kcal/kg LBM/d, P < 0.0001). In stepwise multiple linear regression models, REE explained 13% of variance in spine BMD in women and 6% in men, 33% of variance in hip BMD in women and 22% in men, and 32% of variance in total body BMD in women and 22% in men. In women, weight explained 10% less of the hip BMD variance and 6% less of the total body BMD variance than REE. In men, weight explained 4% more of the spine BMD variance and 1% more of the total body BMD variance than REE.

CONCLUSIONS

REE explained more of the BMD variance than weight in women, and the reverse was true in men. These sex differences were largely explained by sex differences in LBM or weight.

Putative contributors to the secular increase in obesity: exploring the roads less traveled

OBJECTIVE

To investigate plausible contributors to the obesity epidemic beyond the two most commonly suggested factors, reduced physical activity and food marketing practices.

DESIGN

A narrative review of data and published materials that provide evidence of the role of additional putative factors in contributing to the increasing prevalence of obesity.

DATA

Information was drawn from ecological and epidemiological studies of humans, animal studies and studies addressing physiological mechanisms, when available.

RESULTS

For at least 10 putative additional explanations for the increased prevalence of obesity over the recent decades, we found supportive (although not conclusive) evidence that in many cases is as compelling as the evidence for more commonly discussed putative explanations.

CONCLUSION

Undue attention has been devoted to reduced physical activity and food marketing practices as postulated causes for increases in the prevalence of obesity, leading to neglect of other plausible mechanisms and well-intentioned, but potentially ill-founded proposals for reducing obesity rates.

Resting Energy Expenditure: A Better Marker than BMI for BMD in African-American Women

PURPOSE

African-American women tend to be more overweight and to have lower resting energy expenditures (REE) compared with Caucasian women. Weight is associated with bone mineral density (BMD), but the relation between BMD and REE has not been reported.

METHODS

Four hundred postmenopausal African-American women aged 45-87 (yr) from San Diego, CA participated in this community-based cross-sectional study. Body composition (fat mass, lean body mass), bone mineral content (BMC) and BMD of the lumbar spine, hip (femoral neck, greater trochanter, intertrochanter), and total body were measured using dual energy x-ray absorptiometry (DXA). REE was calculated using the Harris-Benedict equation; grip strength was measured by isometric dynamometry.

RESULTS

REE (r range: 0.32-0.79) showed the strongest correlation with spine, total hip, and total body BMC and BMD. In stepwise multiple linear regressions adjusted for age and grip strength, REE explained 15% of the variance in spine BMD, 33% of the variance in total hip, and 32% of the total body BMD variance. REE explained 63% of the total body BMC variance. When body weight replaced REE in the models, weight became the strongest covariate of BMC and BMD but explained 1% less of the variance in spine BMD, 5% less of the variance in total hip BMD, 4% less of the variance in total body BMD, and 3% less of the variances in spine, total hip, and total body BMC than did REE.

CONCLUSION

In this cohort of African-American women, weight explained less of the BMC and BMD variance than REE. Poor energy economy may contribute to being overweight and may explain the lower rates of osteoporosis observed in African-American women.