Bone Mineral Density Response to Caloric Restriction

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Bone Mineral Density Response to Caloric Restriction Essay

It is known that today many people pay special attention to the problem of overweight and obesity. However, not all the people know that weight loss can lead to bone loss. According to the statistical data, bone loss causes more than 1.5 million fractures every year in the USA.Bone Mineral Density Response to Caloric Restriction Essay. Although the vast majority of fractures connected with bone loss are not life-threatening, it is better to take preventive measures in order to avoid bone loss. This paper discusses the problem of bone loss and its consequences. Moreover, the information represented in this paper helps to find out that exercise-induced weight loss accompanies less bone loss compared with caloric restriction weight loss.

Nowadays, many adults in the United States have the problem of overweight. Some dieting experts are sure that “lifestyle modifications, involving low calorie diet and regular exercises” can be the best therapy for obese and overweight people. (Silvermann, 2004, p.72) It is known that body weight can influence body mineral density which is considered to be the major predictor of osteoporotic fractures. Thus, it is found that increased body weight is connected with decreased bone loss, while decreased body weight leads to serious changes in the bones. Besides, increased body weight can cause serious changes in all systems of human body resulting in hypertension, diabetes, heart problems and so on. (Hedley, 2002, p.142)

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The study conducted by the specialists of Washington University School of Medicine prove the fact that weight loss can lead to serious problems with bones, including bone loss, and significant decreases in bone mineral density (BMD). Bone Mineral Density Response to Caloric Restriction Essay. The article Bone Mineral Density Response to Caloric Restriction – Induced Weight Loss or Exercise-induced Weight Loss represents the results of this study. 48 adults, who were divided into three groups: calorie restriction control group, regular exercise group and healthy lifestyle control group, helped to find the answer to the main question of the study. The results proved that body weight can decrease both in CR group and EX group, but it was not changed in HL group. However, calorie restriction caused serious decreases in BMD, while regular exercises helped to preserve body mineral density. The authors of the article state that exercised-induced weight loss has more important advantages over calorie restriction-induced weight loss because it protects against bone loss. Moreover, they recommend everyone who wants to lose weight to combine the above mentioned methods in order to get better results. This study helps to make an effective weight loss program where special attention should be paid to the role of regular exercises. (Villareal, 2006, p.2502)Bone Mineral Density Response to Caloric Restriction Essay.

I completely agree with the authors of the article concerning the significance of body weight control in the life of all people. I think that it is necessary to control the weight of the body and to pay special attention to the food we eat. Of course, it is better to eat only low calorie food which helps to control body weight. (Patlak, 2001, p.321)

Moreover, it is necessary to do physical exercises regularly. Besides, in order to avoid problems with bones, it is recommended to reduce emotional stresses and to eat food which contains much calcium and vitamins, such as nonfat dairy products, green vegetables, ripe fruits, nuts and fish. (Rutherford, 2011, para.4)

References

Hedley, A., Ogden, S., Johnson, S. (2002) Prevalence of Overweight and Obesidy among US Children, Adolescents and Adults. Jama.Vol.292.
Patlak M (2001). Bone builders: the discoveries behind preventing and treating osteoporosis. FASEB J. 15 (10).Bone Mineral Density Response to Caloric Restriction Essay.

Rutherford, H. (2011) What Minerals Are Needed to Prevent Bone Loss? Livestrong.com. July 9, 2011. Retrieved from:< http://www.livestrong.com/article/488205-what-minerals-are-needed-to-prevent-bone-loss/?utm_source=popslideshow&utm_medium=a1>
Silvermann, S. (2004) Osteoporosis self-management: Choices For Better Bone Health. Southern Medical Journal. Retrieved from: http://www.thefreelibrary.com/Osteoporosis+selfmanagement%3a+Choices+For+Better+Bone+Health.-a0119226535
Villareal, D., Fontana, L., Weiss, E., Racette, C., Steger-May, K., Schetchman, K., Klein, S., Holloszy, J. (2006) Bone Mineral Density Response to Caloric Restriction – Induced Weight Loss or Exercise-induced Weight Loss. Arch Intern Med. Vol. 166. Retrieved
from:< http://archinte.ama-assn.org/cgi/reprint/166/22/2502>

Calorie restriction (CR) is promoted to increase longevity, yet this regimen could lead to bone loss and fracture and therefore affect quality of life.

Methods
Forty-six individuals were randomized to 4 groups for 6 months: (1) healthy diet (control group); (2) 25% CR from baseline energy requirements (CR group); (3) 25% energy deficit by a combination of CR and increased aerobic exercise (CR+EX group); and (4) low-calorie diet (890 kcal/d; goal, 15% weight loss) followed by weight maintenance (LCD group). Bone mineral density (total body and hip by dual-energy x-ray absorptiometry) and serum bone markers (bone-specific alkaline phosphatase, osteocalcin, cross-linked C-telopeptide of type I collagen, and cross-linked N-telopeptide of type I collagen) were measured at baseline and after 6 months.

Results
Mean± SE body weight was reduced by -1.0% ± 1.1% (control), -10.4% ± 0.9% (CR), -10.0%±0.8% (CR+EX), and -13.9%±0.7% (LCD). Compared with the control group, none of the groups showed any change in bone mineral density for total body or hip. Bone resorption by serum cross-linked C-telopeptide of type I collagen was increased in all 3 intervention groups, with the largest change observed in the LCD group (CR, 23%±10%; CR+EX, 22%±9%; and LCD, 74%±16% vs control, 4%±10%). Serum levels of cross-linked N-telopeptide of type I collagen were also increased in the LCD group. With regard to bone formation, bone alkaline phosphatase levels were decreased in the CR group (-23%±10%) but were unchanged in the CR+EX, LCD, and control groups.

Conclusions
Moderate CR, with or without exercise, that preserves calcium intake for 6 months leads to large changes in body composition without significant bone loss in young adults. Longer studies with assessments of bone architecture are needed to confirm that CR nutrientdense diets have no deleterious effect on bone health.

Calorie restriction (CR), a dietary intervention that is low in calories but maintains proper nutrition, is the only intervention known to consistently decrease the biologic rate of aging and increase average and maximal life span. Bone Mineral Density Response to Caloric Restriction Essay. The first randomized controlled trial of CR (Comprehensive Assessment of Long-Term Effects of Reducing Intake of Energy [CALERIE]) is being conducted in nonobese men and women. In addition to testing the hypothesis that CR reduces biological aging, assessing the safety of prolonged CR on health, including bone health, is also a primary objective.

Bone mass declines progressively with age in both sexes,1 and it is well known that conditions of chronic energy deficiency impair bone mineral accrual and bone turnover. Furthermore, weight loss in obese individuals is associated with bone loss.2 The Washington University CALERIE study recently reported that a 20% reduction in energy intake sustained for 12 months in middle-aged, nonobese adults can significantly reduce bone mass.3 The reduction in bone mineral density (BMD) (approximately 1.5% overall) at the lumbar spine, total hip, femoral neck, and intertrochanter was correlated with weight loss in the CR group.3

The CALERIE study at Pennington was a 6-month study in which 3 different methods of CR were tested in young, nonobese adults. With regard to aging, we found that 2 of the 3 biomarkers for longevity—fasting insulin concentrations and core body temperature—were reduced with CR, while the levels of dehydroepiandrosterone sulfate were unchanged.4 Also, the metabolic rate was reduced,4 as were risk factors for type 2 diabetes, including insulin sensitivity, visceral fat, and intrahepatic lipid.5 Relevant to bone, body mass was reduced by at least 10% in the intervention groups owing to significant losses of both fat mass and fat-free mass.6 Furthermore, there were significant reductions in fasting concentrations triiodothyronine4 and leptin, providing possible avenues through which bone turnover could be altered. The aims of this analysis were to determine whether (1) CR with adequate nutrition is associated with changes in bone mass and/or bone turnover markers in young adults; (2) changes in bone mass and/or turnover are less pronounced when the same energy deficit is achieved by combining CR with structured aerobic exercise (CR+EX); and (3) changes in bone mass and/or turnover can be explained by changes in body composition or bone trophic factors such as insulin, triiodothyronine, and leptin. Bone Mineral Density Response to Caloric Restriction Essay.

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METHODS
SUBJECTS
Forty-six healthy, overweight men and women completed this study (Table 1). As previously reported, participants were excluded if they smoked; exercised more than twice per week; were pregnant, lactating; or postmenopausal; or had a personal history of obesity (body mass index [calculated as weight in kilograms divided by height in meters squared] never>32), cardiovascular disease, diabetes, or regular use of medications (except birth control). The Pennington Center institutional review board, Baton Rouge, Louisiana, and the Data Safety Monitoring Board of CALERIE approved the study. Subjects provided written informed consent.

Table 1
Anthropometric, Body Composition, and Bone Characteristics of the Subjects at Baselinea
Group
Characteristic Control (n = 11) CR (n = 12) CR + EX (n = 12) LCD (n = 11)
Anthropometric
 Sex, male/female 5/6 6/6 5/7 4/7
 Age, y 37 ± 2 39 ± 2 36 ± 2 39 ± 2
 Weight, kg 81.8 ± 2.8 81.0 ± 3.3 82.0 ± 3.0 81.0 ± 3.3
 BMI 27.3 ± 0.5 27.8 ± 0.5 27.5 ± 0.5 27.5 ± 0.5
Body composition
 Body fat, % 31 ± 2 31 ± 2 33 ± 2 33 ± 2
 Fat mass, kg 25.5 ± 1.2 24.9 ± 1.8 26.4 ± 1.7 26.5 ± 1.9
 Fat-free mass, kg 56.8 ± 3.1 56.3 ± 3.5 55.6 ± 3.5 54.6 ± 3.4
Bone mass
 Total body BMD, g/cm2 1.12 ± 0.02 1.15 ± 0.03 1.08 ± 0.02 1.12 ± 0.02
 Total body BMC, g 2439 ± 93 2475 ± 121 2360 ± 78 2411 ± 102
 Total hip BMD, g/cm2 0.99 ± 0.03 1.07 ± 0.06 0.95 ± 0.02 0.98 ± 0.05
 Total hip BMC, g 34 ± 2 40 ± 4 34 ± 3 35 ± 3
Bone turnover markers
 Formation
  Osteocalcin, ng/mL 14.1 ± 1.2 14.8 ± 1.0 17.3 ± 1.4 13.9 ± 1.1
  Bone alkaline phosphatase, U/L 20.0 ± 2.4 26.1 ± 11.6 23.8 ± 3.0 18.8 ± 2.0
 Resorption
  sNTx, nM BCE/L 23.6 ± 1.6 24.7 ± 1.6 25.8 ± 1.8 23.7 ± 1.7
  sCTx, ng/mL 0.5 ± 0.2 0.6 ± 0.4 0.6 ± 0.1 0.5 ± 0.1
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Abbreviations: BCE, bone collagen equivalents; BMC, bone mineral content; BMI, body mass index (calculated as weight in kilograms divided by height in meters squared); BMD, bone mineral density; CR, calorie restriction; sCTx, serum cross-linked C-telopeptide of type 1 collagen; sNTx, serum cross-linked N-telopeptide of type 1 collagen.

aThe study participants were randomized into 1 of 4 groups for 24 weeks: (1) healthy weight maintenance diet (control group); (2) 25% CR from baseline energy requirements (CR group); (3) 12.5% CR and 12.5% increase in energy expenditure through structured aerobic exercise (CR + EX group); and (4) low-calorie diet (890 kcal/d; goal, 15% weight loss) followed by weight maintenance (LCD group). No group differences were evident at baseline. Values other than sex are presented as mean ± SE. Bone Mineral Density Response to Caloric Restriction Essay.
STUDY DESIGN
Participants were randomized into 1 of 4 groups for 24 weeks: (1) healthy weight maintenance diet (control group); (2) 25% CR from baseline energy requirements (CR group); (3) 12.5% CR and 12.5% increase in energy expenditure through structured aerobic exercise (CR+EX group); and (4) low-calorie diet (890 kcal/d; goal, 15% weight loss) followed by weight maintenance (LCD group). Study outcomes were assessed during a 5-day inpatient stay at baseline and during week 24. Bone Mineral Density Response to Caloric Restriction Essay.

ENERGY PRESCRIPTION
The level of energy intake during the intervention was determined for each individual from an assessment of total daily energy expenditure (using doubly labeled water). This weight maintenance calorie target was then slightly modified according to changes in body weight during 2 weeks of controlled feeding.4

DIETS
All diets were based on the American Heart Association guidelines (30% fat, 15% protein, and 55% carbohydrates) and provided the recommended daily intake for all essential vitamins and minerals. During weeks 1 through 12 and 22 through 24 of the intervention, participants consumed only foods prepared by our metabolic kitchen. During weeks 13 through 22, participants self-selected a diet based on their individual calorie target. Multivitamin and mineral supplements (including calcium) were not permitted.

Dietary intake was estimated from 7-day food records completed at baseline (2 times) and at weeks 4, 10, 14, 16, 18, 20, and 22 of the intervention. Participants received extensive training during screening, including a video, written materials, and feedback from a registered dietician. Inability to complete the food record was an exclusion criterion. The behavioral intervention included weekly training for recording food intake using a weight management system (HMR Calorie System; Health Management Resources, Boston, Massachusetts) and photographic assessment of calorie estimation.7Food records were reviewed weekly, and immediate feedback on the completeness of the record was provided. The records were analyzed for daily calorie and macronutrient content using the Moore Extended Nutrient (MENu) database, which was developed at our center. Bone Mineral Density Response to Caloric Restriction Essay.

EXERCISE
Except for participants in the CR+EX group, participants were not permitted to modify their physical activity pattern. Individuals in the CR+EX group increased their energy expenditure by 12.5% above baseline by undergoing supervised aerobic exercise 5 d/wk. The exercise time necessary to expend the 12.5% calorie target was determined for each individual by indirect calorimetry (V-max; Sensormedics, Yorba Linda, California), and exercise sessions were monitored by heart rate (Polar S-610; Polar Beat, Port Washington, New York).

BEHAVIORAL INTERVENTION
Starting at baseline, participants attended weekly meetings that were conducted not only to teach subjects how to adhere to the diet and exercise plans but also to boost motivation and morale and to comply with the interventions during the outpatient part of the study.

BODY COMPOSITION AND BONE MASS
Body weight was determined by the mean of 2 consecutive measurements that were obtained in the morning after a 12-hour fast and corrected for the weight of a hospital gown. Certified technicians who were blinded to the treatment assignments used dual-energy x-ray absorptiometry (QDR 4500A; Hologic Inc, Bedford, Massachusetts) to measure whole-body fat mass and fat-free mass, total body and right hip BMD, and bone mineral content (BMC). Three assessments were made during baseline (days 0, 14, and 28), and 2 assessments were made at month 6. Intraindividual variability of bone assessments was evaluated from triplicate scans in 46 individuals 14 days apart. The coefficients of variation from the whole-body scans were 0.4%, 0.2%, and 0.5% for BMC, BMD, and bone area, respectively, and 1.1%, 0.5%, and 0.9% for the hip scans (total hip, trochanter, neck of femur, and intertrochanter line).

FASTING SERUM BONE MARKERS
Fasting blood samples were processed immediately, and aliquots were stored at -80°C. As one bone marker may be more sensitive than another for measuring the response to the intervention,8 we selected 2 serum markers of bone resorption— cross-linked C-telopeptide of type I collagen (Serum Crosslaps; Osteometer, Hawthorne, California) and cross-linked N-telopeptide of type I collagen (Osteomark, Princeton, New Jersey)—and 2 serum markers of bone formation—bone-specific alkaline phosphatase (Alkphase-B; Metra Biosystems Inc, Mountain View, California) and osteocalcin (Diagnostic Systems Laboratories, Webster, Texas). All samples from the same participant were analyzed in duplicate within the same assay.Bone Mineral Density Response to Caloric Restriction Essay. The technician was blinded to group assignment. Using the quality-control samples provided with each assay kit, the interassay and intra-assay coefficients of variation were 5.4% and 11.6%, respectively, for cross-linked C-telopeptide of type I collagen; 4.9% and 16.7% (low control) and 9.2% and 8.4% (high control) for cross-linked N-telopeptide of type I collagen; 3.3% and 5.0% (low control) and 1.9% and 2.2% (high control) for bone alkaline phosphatase; and 5.2% and 12.4% (low control) and 12.6% and 13.4% (high control) for osteocalcin. All determinations were within the limits of detection of the assay.

STATISTICAL ANALYSIS
A commercially available statistical software package (Version 9.1; SAS Institute Inc, Cary, North Carolina) was used for analyses. Data are expressed as mean±SE, with the level of significance set at P<.05. At baseline, group, sex, and age effects were tested using a mixed-model analysis of variance (ANOVA). The changes and percent changes from baseline to month 6 were computed for all variables, and ANOVA was performed on the change score to determine differences between groups, with the baseline value and sex as covariates in the model. A linear regression at baseline (n=46×3 scans) was used to generate equations for predicting BMD and BMC from fat-free mass, fat mass, sex, and age. Predicted values for BMD and BMC were calculated at month 6 from the actual values for fat-free mass, fat mass, sex, and age. Differences between the measured and predicted values were tested by ANOVA. The statistical significance for multiple comparisons was adjusted to control for type I errors (Tukey-Kramer method). Relationships between percent changes in BMC, BMD, and biochemical markers of bone turnover vs percent changes in body mass or composition and fasting concentrations of insulin, triiodothyronine, and leptin were determined by Pearson or Spearman correlation coefficients or step-wise regression where appropriate. Bone Mineral Density Response to Caloric Restriction Essay.

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RESULTS
There was an equal distribution of men and women within the 4 groups, and no group differences were observed at baseline for anthropometric, body composition, or bone characteristics (Table 1). At baseline, BMC for the total body and hip was positively associated with body weight (r2=0.53 for total body and r2=0.44 for total hip; P<.001) and fat-free mass (r2=0.66 for total body and r2=0.71 for total hip; P<.001).

The nutrient intakes provided during weight maintenance at baseline and prescribed for CR are summarized in Table 2. By design, there was a reduction in caloric intake for each intervention group. During the second half of the intervention, when participants prepared their own meals at home, 7-day diet records indicated good compliance with the prescribed caloric content of the diets (Table 2). Meals prepared by the metabolic kitchen exceeded all the recommended daily allowances for all essential vitamins and minerals. Calcium intake during ad libitum feeding at baseline was 867±135 mg/d in the CR group, 884±218 mg/d in the CR+EX group, 883±112 mg/d in the LCD group, and 837±87mg/d in the control group. During the self-selected feeding, calcium intake was 898±51 mg/d in the CR group, 1055±89 mg/d in the CR+EX group, 956±69 mg/d in the LCD group, and 1235±118 mg/d in the control group.

Table 2
Energy Content of the Study Dietsa
Mean ± SE (Range), kcal/d
Group Baseline Dietb Prescribed Dietc Self-reported Dietd
Control 2873 ± 151 (2200-3600) 2873 ± 151 (2200-3600) 2623 ± 179 (1549-3072)
CR 2800 ± 158 (2200-3600) 2063 ± 126 (1550-2700) 2061 ± 112 (1523-2643)
CR + EX 2642 ± 136 (2000-3500) 2238 ± 131 (1550-3000) 2114 ± 119 (1494-2764)
LCD 2755 ± 130 (2200-3300) 2091 ± 124 (1650-3000) 2056 ± 129 (1594-3450)
Abbreviations: CR, calorie restriction; LCD, low-calorie diet.

aThe study participants were randomized into 1 of 4 groups for 24 weeks: (1) healthy weight maintenance diet (control group); (2) 25% CR from baseline energy requirements (CR group); (3) 12.5% CR and 12.5% increase in energy expenditure through structured aerobic exercise (CR + EX group); and (4) low-calorie diet (890 kcal/d; goal, 15% weight loss) followed by weight maintenance (LCD group).Bone Mineral Density Response to Caloric Restriction Essay. No group differences were evident at baseline.
bThe energy intake at baseline was calculated from two 14-day doubly labeled water assessments of daily energy expenditure and weight fluctuations during 14 days of controlled feeding.
cThe amount of energy prescribed during the 6-month intervention. The diet was prepared by the metabolic kitchen for months 0 through 3. Breakfast and dinner were consumed at the center, and lunch and an evening snack were packaged for takeout.
dDuring months 4 through 6, participants were required to follow their prescribed intervention diet. The data shown are the averages of 7-day diet records collected at weeks 14, 16, 18, 20, and 22.
As previously reported,4,6 after 6 months the body weight (Figure 1) was reduced in the CR group (-10.4±0.9%), the CR+EX group (-10.0%±0.8%), and the LCD group (-13.9%±0.7%) compared with the control group, and each intervention group had significant losses of fat mass (CR, -24%±3%; CR+EX, -25%±3%; and LCD, -32%±3%) and fat-free mass (CR, -5%±1%; CR+EX, -3%±1%; and LCD, -6%±1%). Fasting insulin concentrations were significantly reduced in all 3 calorie-restricted groups at month 6 compared with baseline and the control group (CR, -29%±6%; CR+EX, -20%±12%; LCD, -18%±8%; and control, 0%±8%; treatment effect, P<.03). Similarly, fasting leptin (CR, -39%±10%; CR+EX, -52%±8%; LCD, -54%±5%; and control, -2%±8%; treatment effect, P<.005) and triiodothyronine (CR, -6%±3%; CR+EX, -12%±3%; LCD, -14% ± 3%; and control, 4% ± 3%; treatment effect, P<.001) concentrations were reduced in all intervention groups compared with baseline and the control group. Bone Mineral Density Response to Caloric Restriction Essay.

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Figure 1
Effect of different modes of calorie restriction (CR) on weight as previously shown4,6 (A) and body composition changes (fat mass and fat-free mass) (B) after 24 weeks. The study participants were randomized into 1 of 4 groups for 24 weeks: (1) healthy weight maintenance diet (control group); (2) 25% CR from baseline energy requirements (CR group); (3) 12.5% CR and 12.5% increase in energy expenditure through structured aerobic exercise (CR+EX group); and (4) low-calorie diet (890 kcal/d; goal, 15% weight loss) followed by weight maintenance (LCD group).

Compared with the control group, no significant effect of treatment was observed for the changes in BMD (Figure 2) and BMC assessed for total body and right hip. In the CR group, total-body BMD increased significantly from baseline by 1.7%±0.7% (P=.001) but was not different from that in the control group (P=.12). To determine whether the changes in BMC and BMD at month 6 were expected based on individual changes in body composition (fat-free mass and fat mass), we compared the actual BMC and BMD measured by dual-energy x-ray absorptiometry with the BMC and BMD derived from theprediction equation at baseline. For both BMD and BMC, there was no significant difference between the actual value measured by dual-energy x-ray absorptiometry and the value derived from the regression model in any group (BMD results shown as actual vs predicted: CR, 1.17±0.1 g/cm2 vs 1.12±0.03 g/cm2; CR+EX, 1.09±0.06 g/cm2 vs 1.12±0.04 g/cm2; LCD, 1.13±0.08 g/cm2 vs 1.12±0.04 g/cm2; and control, 1.12±0.08 g/cm2 vs 1.12±0.03 g/cm2). Bone Mineral Density Response to Caloric Restriction Essay.