|Home | About | Journals | Submit | Contact Us | Français|
Obese and sedentary persons have increased risk for cancer; inflammation is a hypothesized mechanism. We examined the effects of a caloric restriction weight loss diet and exercise on inflammatory biomarkers in 439 women. Overweight and obese postmenopausal women were randomized to 1-year: caloric restriction diet (goal of 10% weight loss, N=118), aerobic exercise (225 minutes/week of moderate-to-vigorous activity, N=117), combined diet+exercise (N=117) or control (N=87). Baseline and 1-year high-sensitivity C-reactive protein (hs-CRP), serum amyloid A (SAA), interleukin-6 (IL-6), leukocyte and neutrophil levels were measured by investigators blind to group. Inflammatory biomarker changes were compared using generalized estimating equations. Models were adjusted for baseline body mass index (BMI), race/ethnicity and age. 438 (N=1 in diet+exercise group was excluded) were analyzed. Relative to controls, hs-CRP decreased by geometric mean (95% confidence interval, p-value) 0.92mg/L (0.53–1.31, P<0.001) in the diet and 0.87mg/L (0.51–1.23, P<0.0001) in the diet+exercise groups. IL-6 decreased by 0.34pg/ml (0.13–0.55, P=0.001) in the diet and 0.32pg/ml (0.15–0.49, P<0.001) in the diet+exercise groups. Neutrophil counts decreased by 0.31×109/L (0.09–0.54, P=0.006) in the diet and 0.30×109/L (0.09–0.50, P=0.005) in the diet+exercise groups. Diet and diet+exercise participants with ≥5% weight loss reduced inflammatory biomarkers (hs-CRP, SAA, and IL-6) compared to controls. The diet and diet+exercise groups reduced hs-CRP in all subgroups of baseline BMI, waist circumference, CRP level, and fasting glucose. Our findings indicate that a caloric restriction weight loss diet with or without exercise reduces biomarkers of inflammation in postmenopausal women, with potential clinical significance for cancer risk reduction.
Approximately 25% of cancers are due to overweight or obesity and a sedentary lifestyle (1), risk factors which are particularly common in older women (2, 3). A meta-analysis of 31 studies estimated that each 5 kg/m2 increase in BMI was associated with a 12% increased risk of postmenopausal breast cancer (relative risk= 1.12, 95% confidence interval [CI]=1.08–1.16) (4). Obesity is an established risk factor for endometrial cancer; three-quarters of these cases occur in postmenopausal women (5). Increased age and obesity are risk factors for several additional cancers that affect women including colon, pancreas, kidney, and lower esophageal (4, 6). Thus weight loss interventions may be important for reducing risk for several cancers in postmenopausal women.
Obesity and a sedentary lifestyle may affect cancer risk through several mechanisms including effects on inflammatory pathways (1). Individuals with chronic infectious disease and inflammatory conditions are at increased risk for several cancers (7). Repeated tissue damage by reactive nitrogen and oxygen species produced from leukocytes and other inflammatory cells induces DNA damage and gene mutations which initiate carcinogenesis (7). DNA damage resulting from chronic inflammation was shown to affect several critical pathways regulating cellular homeostatsis (e.g., cell cycle regulation, apoptosis, DNA repair systems) (8). Elevated inflammatory biomarkers such as C-reactive protein (CRP) and interleukin 6 (IL-6) are associated with increased risk for several cancers including breast (9), colon (10), lung (11), and endometrium (12, 13), although not all studies have shown an association (10, 11).
Further support for a role of inflammation in cancer is the observed association between use of non-steroidal anti-inflammatory drugs (NSAIDS) and reduced risk for breast, colon, stomach, esophagus, and other cancers (14). NSAIDS including aspirin have been investigated as risk reduction strategies against several cancers, but have risk of adverse effects (14). Statins also reduce CRP (15), but have some side effects (16) and were not protective against cancer in a meta-analysis of clinical trials (16). Because blood levels of inflammatory biomarkers increase with age (17), obesity (18) and menopause (19), investigating lower-risk, non-pharmacological methods for reducing inflammatory biomarkers may identify feasible methods for reducing cancer risk among overweight and obese postmenopausal women.
Obesity and low cardiopulmonary fitness are associated with increased blood levels of CRP (18). A systematic review concluded that weight loss through various mechanisms reduces CRP (20). Most of the reviewed studies were short-term, however, and few of the cited studies looked at other cancer-related inflammatory biomarkers. Previous longer-term (12 or more months) weight loss trials have been conducted in individuals with chronic diseases (21, 22), elevated cardiovascular disease risk (23) and impaired glucose tolerance (24) or in premenopausal women (25), and have not focused on overweight or obese postmenopausal women, a group at increased risk for several types of cancer including breast, colon, endometrium and other obesity-related cancers (4, 5). Therefore, weight loss effects with and without exercise on inflammatory biomarkers over ≥12 months require further investigation in this population.
Experimental models suggest that exercise could independently affect blood levels of inflammatory biomarkers through increased IL-6 release from skeletal muscle (26). Most studies have not shown an effect of exercise without weight loss on inflammatory biomarkers, however (27–30).
Leukocyte and neutrophil counts are clinical indicators of inflammation, and leukocyte counts are positively associated with cancer incidence and mortality in postmenopausal women (31). However, little is known about the effects of dietary weight loss and exercise on leukocyte and neutrophil counts in postmenopausal women.
Statin and anti-inflammatory medications could reduce inflammatory biomarkers (32). However, few studies have examined whether the use of these medications modifies effects of dietary weight loss and exercise on inflammatory biomarkers (22).
This study examined the independent and combined effects of caloric restriction weight loss diet and exercise interventions on inflammatory biomarkers (high-sensitivity CRP [hs-CRP], serum amyloid A [SAA], IL-6, and leukocyte and neutrophil counts) in overweight and obese, postmenopausal women. We also examined mediators (weight loss, exercise and diet adherence) and potential moderators (baseline characteristics and use of medications that may affect inflammation [statins and NSAID] (32)) of intervention effects on inflammatory biomarkers.
The Nutrition and Exercise for Women (NEW) study was a 12-month, randomized controlled trial conducted from 2005 to 2009 which was initially funded to examine the effects of a caloric restriction weight loss diet, aerobic exercise, and combined caloric restriction diet+exercise interventions on cancer biomarkers. The primary outcome was serum estrone. Secondary outcomes were additional sex hormones, glucose metabolism, mammogram density, body composition, quality of life, and complete blood count including leukocyte and neutrophil counts. An ancillary study was conducted to assess the interventions’ effects on inflammatory biomarkers (hs-CRP, SAA, IL-6).
The NEW trial was designed to enroll 503 participants in order to have at least 80% power for a 0.05/3-level (Bonferroni corrected) test to detect a difference of 10% in estrone changes over a 12-month period making three primary pairwise comparisons: diet+exercise vs. exercise; diet+exercise vs. diet; and diet vs. exercise groups. Because of funding limitations and expected adherence and retention, after half of the women completed 12 months, we recalculated power estimates which indicated sufficient power to detect primary and secondary endpoint changes with a sample size of 439. Participants were recruited from the greater Seattle area through targeted mass mailings, media placements, and community outreach (Figure 1). The study design and recruitment process (33), and intervention effects on weight (33), body composition (33), quality of life (34) and serum insulin (35), glucose (35), and vitamin D (36) have been reported elsewhere. Eligibility criteria included: 50–75 years; body mass index (BMI) ≥25.0 kg/m2 (if Asian-American ≥23.0 kg/m2); <100 minutes/week of moderate activity; postmenopausal; not taking postmenopausal hormone therapy for the past 3 months; no history of breast cancer, heart disease, diabetes mellitus, or other serious medical conditions; fasting glucose <126 mg/dL; non-smoking; alcohol intake of ≤2 drinks/day; able to attend intervention sessions at the study facility; and a normal exercise tolerance test. The study procedures were reviewed and approved by the Fred Hutchinson Cancer Research Center Institutional Review Board. All participants provided signed Informed Consent.
A total of 439 women were randomized to: caloric restriction diet with a goal of 10% weight reduction (N=118), moderate-to-vigorous intensity aerobic exercise for 45 minutes/day, 5 days/week (N=117), combined exercise and diet (N=117), or control group (N=87). Random allocation sequences were generated by a computer-based program developed by the study statistician with stratification by BMI (<30.0, ≥30.0 kg/m2) and race/ethnicity (non-Hispanic White, Black, other). To allocate a smaller number of women to the control group, we used permuted blocks randomization with a block size of 4 where control assignment was eliminated with a probability of 1 in 4. The sequence was concealed until the allocation was determined. Study staff enrolled the participants and assigned them to an intervention or the control group. Study staff involved in assessments and investigators other than statisticians were blinded to randomization status.
The caloric restriction diet intervention was a modification of the Diabetes Prevention Program (37) and the Look AHEAD trial lifestyle interventions (38) with goals of: caloric intake of 1200–2000 kcal/day based on weight, ≤30% calories from fat, 10% weight loss within the first 24 weeks, and maintenance thereafter. The diet intervention was conducted by dietitians with training in behavior modification. Participants had 2–4 individual sessions with the dietitians, then met weekly in groups (5–10 women) until week 24, and afterward attended monthly group sessions in addition to email or phone contacts. The diet+exercise group’s diet sessions were separate from those of the diet-only group.
The goal of the exercise intervention was 225 minutes/week of moderate-to-vigorous intensity exercise for 12 months. Participants attended 3 supervised sessions/week at the facility and 2/week at home. At both facility and home exercise sessions, participants wore Polar heart rate monitors (Polar Electro, Lake Success, NY). They gradually increased exercise training to 70–85% of maximal heart rate (as determined during the baseline VO2max treadmill test) for 45 minutes per session by week 7 and maintained thereafter. Exercise mode, duration, peak heart rate, and perceived exertion were recorded at each session in facility and home activity logs for all 12 months. Activities with ≥4 metabolic equivalents were counted towards the prescribed exercise target (33). Participants used treadmills, ellipticals, rowing machines and stationary bikes during the facility exercise sessions; walking was the most common home exercise. Exercise-only and diet-only participants were asked not to change their diet and exercise habits, respectively.
Controls were asked not to change their diet or exercise habits. After 12-months, controls were offered 4 group diet sessions and 8 weeks of supervised exercise sessions.
Demographics, medication use, lifestyle behaviors, anthropometrics and cardiopulmonary fitness were assessed at baseline and 12 months. Demographic information was assessed using standard questionnaires. Participants brought current prescription and over-the-counter medication bottles to clinic visits. Participants taking statin or NSAIDS (including over-the-counter) medications at baseline were classified as users. Past 3 months type, intensity and duration of physical activity were assessed (33). All participants wore pedometers (Accusplit, Silicon Valley, CA) and recorded steps for 7 consecutive days at baseline, 6- and 12 months. A food frequency questionnaire assessed usual dietary intake (33). Intervention women completed daily diet logs (for the first 6 months) and/or facility and home activity logs (for all 12 months), depending on assigned group.
Height and weight were measured with a stadiometer and standard scale, and BMI was calculated as kg/m2. Waist circumference was measured to the nearest 0.5 cm at the end of normal expiration at the minimal waist. Body fat was measured by a dual-energy X-ray absorptiometry whole-body scanner (GE Lunar, Madison, WI). Cardiopulmonary fitness was assessed using a modified branching treadmill protocol monitored by a MedGraphics automated cart (MedGraphics, St. Paul, MN) (33).
Blood samples were collected at baseline and 12 months after 12 hour fasting and no exercise for 24 hours. Samples were processed within an hour, and serum was stored at −70C. Serum hs-CRP and SAA were analyzed at the University of Washington, Department of Laboratory Medicine (M.H.W.). Serum IL-6, insulin, and glucose were analyzed at the Northwest Lipid Research Laboratories at the University of Washington. Hs-CRP and SAA were measured using assay kits from Siemens Healthcare Diagnostics Products GmbH (Marburg, Germany). IL-6 was measured by an ultrasensitive solid-phase sandwich enzyme-linked immunosorbent assay on a high sensitivity human IL-6 Immunoassay kit (R&D Systems, Inc, Minneapolis, MN). The lower detection limits were 0.2 mg/L, 0.7 mg/L, and 0.039 pg/mL for hs-CRP, SAA and IL-6, respectively. Intra- and inter-batch coefficients of variation (CV) were as follows: hs-CRP (4.1, 4.7%), SAA (5.4, 6.2%) and IL-6 (9.7, 12.4%). Glucose and insulin were measured using a Clinical Chemistry Autoanalyzer by hexokinase method and a polyethylene glycol-accelerated, double antibody radioimmunoassay (39), respectively. The intra- and inter-assay CVs for glucose were 1.1% and 3.5%, respectively. The intra-assay CV was 4.5% for insulin. Homeostasis assessment–insulin resistance (HOMA-IR= fasting insulin [mU/L] × fasting glucose [mmol/L]/22.5) was calculated (35). Serum samples were analyzed in batches and each participant’s samples were assayed in the same batch. The number of samples from each study arm was approximately equal and participant randomization dates were similar within each batch. Whole blood for complete blood counts was collected and stored at room temperature. Leukocyte and neutrophil counts were analyzed at Quest Diagnostics Inc (Seattle, WA) on the same day.
Baseline characteristics between women who completed 12-month assessments (completers) and those who did not (non-completers) were compared using a Chi-square test and t-tests. All randomized participants were included in the analysis (intention-to-treat). We conducted additional analyses eliminating individuals with extremely high hs-CRP values (≥20.0 mg/L, above 99%tile) at baseline or 12 months. There were no differences between completers and non-completers by group assignments, most baseline characteristics or inflammatory biomarkers (Supplement table 1). Based on our understanding of the drop-out reasons (Figure 1), the follow-up outcomes did not appear to have a non-ignorable missing data mechanism (informative missingness). Thus, missing data were imputed by multiple imputation using PROC MI (SAS Institute, Cary, NC). Inflammatory biomarkers were imputed based on age, race/ethnicity, BMI and baseline values of each inflammatory biomarker. Five imputed datasets were created (40), and results were combined by PROC MIANALYZE. We also conducted the analyses using available data and last observation carried forward. No substantive differences were observed among these methods, and therefore we present only the results from the multiple imputation method. Results of the main analyses using available data are presented in Supplementary Table 6.
The primary analysis compared 12-month changes using a generalized estimating equation approach to account for repeated assessments on the same subjects: E(Y)= α + β1*Group + β2*Time + β3*Group*Time + β4*Z + β5*Z*Time, where E(Y)= expected value of an inflammatory outcome variable Y, Z= covariates (41). All models were adjusted for randomization strata (i.e., baseline BMI [<30, ≥30 kg/m2] and race/ethnicity [White, Black, and others]) and age, except for the subgroup analyses stratified by baseline age (≤60, >60 years old) and BMI (<30, ≥30 kg/m2). Age was included as a covariate because of its associations with CRP (17). Adjusted and unadjusted results were very similar, and therefore we present only the adjusted model. We used the Bonferroni correction to adjust for multiple comparisons (e.g., two-sided alfa=0.05/6=0.008 for 6 comparisons) for the primary analysis. Treatment effects were calculated as relative differences to the control group in absolute and percent changes in inflammatory biomarkers from baseline to 12 months, with 95% CIs.
The secondary analyses examined the intervention effects stratified by four adherence measures (weight loss, exercise adherence [minutes/week], diet session attendance, and changes in percent calorie intake from fat), and by baseline characteristics and medication use. We created subgroups based on weight loss during the trial (lost <5%, ≥5% of baseline body weight) within each intervention arm and compared 12-month changes in inflammation in these subgroups to the control group. Participants with missing 12-month weight were classified as ‘lost <5%’. Five percent was used as a cutpoint, because few participants in the exercise group lost ≥5% of body weight and 5% weight loss is a common clinical endpoint (42). Tertiles were used as cutpoints for other adherence variables. We also stratified by baseline age (≤60, >60 years old), BMI (<30, ≥30 kg/m2) (43), waist circumference (<88, ≥88 cm) (44), CRP risk category (≤3, >3 mg/L) (45), insulin resistance defined by a median HOMA-IR (<2.7, ≥2.7), fasting glucose (<100, ≥100 mg/dL) (44), and use of medications with anti-inflammatory properties (statins and NSAIDS) (32), because of their clinical importance. Interactions between stratification (baseline characteristics) × intervention effects were tested in the models to assess effect modification. Additionally, we compared the changes in inflammatory biomarkers between caloric restriction diet (diet and diet+exercise groups) vs. no caloric restriction diet (exercise and control groups); and exercise (exercise and diet+exercise groups) vs. no exercise (diet and control groups).
All outcome variables were log-transformed, due to skewed distributions of the original variables. Geometric means of outcome variables were reported unless otherwise described. All analyses were performed with SAS software version 9.2.
Of 439 women randomized, baseline serum samples were available from 438 participants. One participant did not have data for baseline neutrophil counts. A total of 399 (90.9%) of randomized participants returned for a 12-month blood draw. Twenty women dropped the intervention during weeks 0–24, 6 during weeks 25–48, and 13 did not return for the 12-months assessment. The numbers of non-completers in each group did not differ across the groups (P=0.72). Likelihood of bias from missing data was considered minimal because of the low drop-out rate (N=39, 9%), and because there were no statistically significant differences by group assignments, baseline characteristics or inflammatory biomarkers between completers and non-completers of 12-month assessments except for waist circumference (Supplement Table 1).
Baseline characteristics are displayed in Table 1. The arithmetic mean of baseline hs-CRP was 3.57 mg/L. Data on weight at 6 months were available for 387 women (74 in control, 107 in diet, 94 in exercise, 112 in diet+exercise). Weight losses at 6 months were 0.1 (3.6) kg in the control, 6.6 (5.0) kg in the diet, 1.0 (5.6) kg in the exercise, and 7.5 (3.8) kg in the diet+exercise group. At 6 months 41.5% (N=49) in the diet, 21.4% (N=25) in the exercise, and 46.2% (N=54) in the diet+exercise groups lost ≥10% of baseline weight. Inflammatory biomarkers were not measured at 6 months.
Results of the intervention effects on body composition at 12 months have been published elsewhere (33). Briefly, the diet, exercise, and diet+exercise groups decreased weight by 8.5% (P<0.01), 2.4% (P=0.03) and 10.8% (P<0.01), respectively, compared with controls. Waist circumference decreased in diet (−4.4 cm, P<0.01), exercise (−2.0 cm, P=0.02), and diet+exercise (−7.0 cm, P<0.01) groups compared to controls (+1.1 cm). All intervention groups decreased percent body fat (Δdiet= −4.2%, P<0.01; Δexercise= −1.6%, P<0.01; Δdiet+exercise= −5.9%, P<0.01) compared with controls. At 12 months 41.5% (N=49) in the diet, 3.8% (N=4) in the exercise, and 59.5% (N=69) in the diet+exercise groups lost ≥10% of baseline weight. The exercise and diet+exercise groups completed a mean 80.2% and 84.7% of the exercise goal (225 minutes/week). The exercise and diet+exercise groups increased pedometer counts by 2415 steps/day (P<0.01, vs. controls) and 3468 steps/day (P<0.01, vs. controls), respectively. Aerobic fitness increased by 0.17 L/min (P<0.01) and 0.12 L/min (P<0.01), respectively in the exercise and diet+exercise groups (vs. control).
The diet and diet+exercise groups experienced marked and significant decreases in most inflammatory biomarkers compared with controls (Table 2). Compared to controls, hs-CRP decreased by 0.92 mg/L (36.1%, P<0.001) in the diet group, and by 0.87mg/L (41.7%, P<0.001) in the diet+exercise group. IL-6 decreased by 0.34 pg/ml (23.1%, P=0.001 vs. control) in the diet group and by 0.32 pg/ml (24.3%, P<0.001 vs. control) in the diet+exercise group. Neutrophil counts reduced by 0.31×109/L (9.6%, P=0.006) in the diet group and by 0.30×109/L (9.0%, P=0.005) in the diet+exercise group (vs. control). SAA decreased, by 0.82 mg/L (17.5%), in the diet group (P=0.005 vs. control). Leukocyte counts reduced, by 0.41×109/L (7.2%), in the diet+exercise group (P=0.001 vs. control). There were no significant differences between the diet and diet+exercise groups, or between the exercise and control groups, in any inflammatory biomarker. The results were similar when women with hs-CRP ≥20.0 mg/L (N=5 in exercise, N=1 in diet, N=2 in diet+exercise groups) were excluded (Supplement Table 2).
Compared to controls, participants who lost ≥5% of baseline weight reduced hs-CRP by 49.5% in the diet (P<0.001) and by 49.2% in the diet+exercise groups (P<0.001, Table 3). No differences were observed among those who lost <5% of baseline weight. In the diet and diet+exercise groups, women who lost ≥5% of baseline weight reduced SAA (P<0.001 for diet, P=0.016 for diet+exercise), and IL-6 (P<0.001 for diet, P<0.001 for diet+exercise) compared to controls. In the diet+exercise group, leukocyte and neutrophil counts significantly reduced among women who lost ≥5% of weight. Although exercisers who lost ≥5% of baseline weight reduced hs-CRP by 19.1%, the effect did not reach statistical significance (P=0.088 vs. control). When we eliminated data from women with hs-CRP ≥20.0 mg/L, we observed a decrease in hs-CRP among exercisers who lost ≥5% of baseline weight (Δ= −25.1%, P=0.005 vs. controls, Supplement Table 3).
In the exercise group, there were no associations between exercise adherence (weekly minutes of exercise) and inflammatory biomarkers (Table 4). In the diet+exercise group, women significantly reduced hs-CRP in all tertile groups of exercise adherence compared to controls. The middle and highest tertile groups significantly reduced IL-6 and leukocyte and neutrophil counts compared to controls in the diet+exercise group.
Twelve-month changes in inflammatory biomarkers stratified by diet adherence (session attendance and 12-month changes in percent calorie intake from fat) are presented in Table 5. In the diet group, both the middle and highest tertile groups of diet session attendance significantly reduced hs-CRP (Δmiddle= −43.9%, Δhighest= −49.4%), SAA (Δmiddle= −17.7%, Δhighest= −30.8%), IL-6 (Δmiddle= −24.6%, Δhighest= −33.3%) and neutrophil counts (Δmiddle= −8.9%, Δhighest= −11.0%) compared to controls, with greater reductions in the highest tertile group. In the diet+exercise group the middle and highest tertile groups of diet session attendance significantly reduced hs-CRP (Δmiddle= −44.9%, Δhighest= −47.3%), IL-6 (Δmiddle= −25.7%, Δhighest= −28.9%) and leukocyte (Δmiddle= −8.2%, Δhighest= −7.2%) and neutrophil (Δmiddle= −10.0%, Δhighest= −8.2%) counts compared to controls.
In the diet and diet+exercise groups, hs-CRP and IL-6 significantly reduced in all tertile groups of changes in percent calorie intake from fat. Reductions in hs-CRP tended to be greater in higher tertile groups in both diet (Δlowest= −27.1%, Δmiddle= −35.9%, Δhighest= −51.9%) and diet+exercise (Δlowest= −26.8%, Δmiddle= −38.5%, Δhighest= −51.6%) groups.
Intervention effects on hs-CRP were independent of baseline age, BMI, hs-CRP level, HOMA-IR, fasting glucose, and statin use (interaction P>0.05, Table 6). The reduction in hs-CRP among women with baseline waist circumference (≥88 cm) was greater than those with baseline waist circumference (<88 cm) (interaction P=0.012). The diet and diet+exercise groups reduced mean hs-CRP only among individuals not taking NSAIDS at baseline (vs. controls).
Women in the caloric restriction weight loss diet intervention groups (diet and diet+exercise groups) significantly reduced all inflammatory biomarkers compared to those not in a diet intervention (exercise and control groups) (Supplement Table 4). Those in the exercise intervention groups (exercise and diet+exercise groups) did not reduce any inflammatory biomarkers compared with those not in an exercise intervention (diet and control groups, Supplement Table 5).
This study found that a 12-month caloric restriction weight loss diet intervention, with or without exercise, produced large, significant reductions in several biomarkers of inflammation. This trial tested a caloric restriction diet intervention consistent with the recommendations of the NIH Obesity Education Initiative Expert Panel (calorie reduction of 500–1000 kcal/day), and an exercise intervention consistent with federal guidelines for physical activity (30–45 minutes/day of moderate or greater intensity activity, ≥5 days/week) (43, 46). Our caloric restriction diet intervention groups experienced mean weight losses of 9–11% (33). The exercise and diet+exercise groups, respectively completed mean (SD) 163.3 (70.6) and 171.7 (62.7) minutes/week of moderate-to-vigorous intensity activity (target 225 minutes/week). These results suggest that modest amounts of weight loss can have large beneficial effects on clinically-relevant inflammatory biomarkers, which could impact risk reduction of several cancers in overweight or obese, postmenopausal women.
A systematic review of 33 intervention studies has shown that each 1kg of weight loss corresponds to 0.13 mg/L reduction in CRP (20). The mean weight loss in our diet+exercise group was 8.9 kg. The expected mean reduction of 1.157 mg/L in CRP is consistent with our observed mean reduction of 1.05 mg/L ([hs-CRP outliers ≥20 mg/L, N=2] were removed from this estimate).
A small number of studies have investigated the long-term (12 months or more) combined and independent effects of dietary weight loss and exercise on inflammatory biomarkers. In an 18-month randomized controlled trial among 316 older (≥60 years old), overweight or obese adults with knee osteoarthritis, dietary weight loss with or without exercise, but not exercise-alone, reduced CRP and IL-6 particularly in men (21), similar to the findings in our study. Another 12-month randomized controlled trial comparing individual and combined effects of low-fat diet and/or exercise programs among 274 adults found that diet with or without exercise significantly reduced CRP only among postmenopausal women with metabolic syndrome (23).
In our study, higher adherence to the caloric restriction diet intervention, whether measured by weight loss, session attendance, or reduction in percent calories from fat, was associated with greater reductions in hs-CRP. Conversely, no associations were observed between exercise adherence and inflammatory biomarkers. Direct comparisons of diet vs. no diet groups showed significant reduction in all inflammatory biomarkers in the diet groups.
We found that hs-CRP decreased to the greatest degree in women who lost ≥5% of baseline weight regardless of intervention group. Trials testing lifestyle interventions to produce weight loss in other populations, including persons with impaired glucose tolerance, type 2 diabetes, and premenopausal women, have found significant correlations between changes in BMI and inflammatory biomarkers (e.g., CRP, IL-6) over 1–2 years (22, 24, 25).
Previous meta-analyses and reviews support a lack of effect of either short- or long-term aerobic exercise on inflammatory biomarkers in the absence of weight loss (28, 47). Among 115 overweight or obese postmenopausal women, we found significant linear trends of greater weight loss associated with a larger decrease in CRP during a 12-month exercise trial in which exercisers attained a mean 171 minutes/week (30). Similarly, a 6-month trial designed to test exercise dose (70–120 minutes/week) on CRP in 464 overweight and obese postmenopausal women found that exercise decreased mean CRP only in women with ≥2.6 kg weight loss (28).
There is little information on long-term effects of other types of exercise on inflammatory biomarkers. Two randomized clinical trials showed measureable declines in CRP over 4–12 months with resistance exercise compared with controls in diabetic men (48) or in premenopausal women (49). Therefore, the effects on inflammatory biomarkers of resistance training alone or combined with aerobic exercise, in postmenopausal women are unknown.
Representative population data show positive associations between adiposity and leukocyte counts (50). To our knowledge, our study is the first investigation reporting long-term (12 months) effects of a caloric restriction weight loss diet with and without exercise on leukocyte and neutrophil counts. Leukocyte and neutrophil counts decreased in the diet and diet+exercise, but not exercise, groups. We also found reduced leukocyte and neutrophil counts among individuals who lost ≥5% of initial weight in the diet+exercise groups. However, leukocytes and neutrophil counts reduced in women with <5% weight loss in the diet group. Future studies are required to understand effects and underlying mechanisms of caloric restriction weight loss diet and exercise interventions on leukocyte and neutrophil counts.
We found no difference in intervention effects on inflammatory biomarkers in statin users and nonusers. A meta-analysis of 65 statin intervention studies concluded that statin reduced CRP by 30.8% (95%CI=22.3–39.4%) (15). In our study, women in the diet and diet+exercise groups decreased hs-CRP by 36–42%, similar to the highest impact of statins. In addition, these women significantly reduced hs-CRP independent of statin use at baseline, consistent with results from the LookAHEAD trial in type 2 diabetes patients (22). Our results suggest that weight loss through a caloric restriction diet with or without exercise could have additive effects on pharmacological treatments for reducing inflammation.
Our observed 40% reductions in hs-CRP in the diet and diet+exercise groups could be expected to reduce breast, endometrial and other cancer risks in postmenopausal women. A meta-analysis of 8 case-control and 6 cohort studies concluded that each log unit increase in CRP was associated with increase in overall cancer risk (random effects risk estimate=1.10, 95%CI=1.02–1.18) and lung cancer risk (random effects risk estimate=1.32, 95%CI=1.08–1.61) (11). In a cohort of 4209 women aged 55 years and older, women with CRP levels between 3–10 mg/L had a 60% increased risk of breast cancer (hazard ratio=1.59, 95%CI=1.05–2.41) compared with those with CRP <1 mg/L (9). A nested case-control study within the Women’s Health Initiative observational cohort found that non-hormone users in the highest CRP quartile (>3.33 mg/L) had a greater than doubling of risk (hazard ratio=2.29, 95%CI=1.13–4.65) for endometrial cancer compared to women in the lowest CRP quartile (<0.64 mg/L) (12).
Strengths of this study include: a large sample size, a randomized controlled trial design, three intervention arms, long duration of the intervention (12 months), high retention (91%), high adherence to intervention prescriptions, and multiple measures of inflammation.
There were several limitations. Our study sample was highly selected (e.g., inclusion criteria and intervention requirements) which may limit the generalizablity. The trial sample of overweight and obese postmenopausal women was relatively homogeneous sample, which may limit the generalizability for other race or ethnic groups, for normal-weight or younger women, or for men. However, our sample represents a large segment of the population who are at increased risk for several cancers. We tested only one dietary weight loss program and one exercise program, and therefore cannot extend results to other dietary patterns or exercise modalities. However, our diet intervention was based on the known weight loss efficacy of the Diabetes Prevention Program (37) and Look AHEAD interventions (38). Thus, our findings provide critical evidence on the benefits of weight loss and exercise lifestyle change interventions for reducing inflammatory biomarkers in postmenopausal women.
In conclusion, our findings support weight loss through calorie reduction and increased exercise as a means for reducing inflammatory biomarkers, and thereby potentially reducing cancer risk in overweight and obese postmenopausal women.
The Nutrition and Exercise for Women (NEW) trial was supported by R01 CA105204-01A1 and U54-CA116847 from National Cancer Institute (NCI). Part of this study was conducted at the University of Washington, Clinical Nutrition Research Unit supported by National Institute of Diabetes and Digestive and Kidney Disease (NIDDK) 61-7015. AK was supported by NCI R25CA094880 at the time of this study and is currently supported by NCI 2R25CA057699. While working on the trial, CMA was employed at the Ohio State University, and located to NCI following completion of her effort on the NEW trial. KEF was supported by 5KL2RR025015-03 from National Center for Research Resources (NCRR), a component of the National Institute of Health (NIH) and NIH Roadmap for Medical Research. CEM is supported by a fellowship from the Canadian Institutes of Health Research (CIHR).
We wish to thank the NEW study participants for their time and effort in the trial.
This study was supported by R01 CA105204-01A1 and U54-CA116847 from National Cancer Institute (NCI). Part of this study was conducted at the University of Washington, Clinical Nutrition Research Unit supported by National Institute of Diabetes and Digestive and Kidney Disease 61-7015. AK was supported by NCI R25CA094880 at the time of this study and is currently supported by NCI 2R25CA057699. While working on the trial, CMA was employed at the Ohio State University, and located to NCI following completion of her effort on the NEW trial. KEF was supported by 5KL2RR025015-03 from National Center for Research Resources, a component of the National Institute of Health (NIH) and NIH Roadmap for Medical Research. CEM is supported by a fellowship from the Canadian Institutes of Health Research.
Conflicts of interest: The authors have no conflicts of interest to disclose.
Trial Registration: ClinicalTrials.gov NCT00470119