Improved nutritional status and bone health after diet-induced weight loss in sedentary osteoarthritis patients: a prospective cohort study
Abstract
BACKGROUND/OBJECTIVES: Obese subjects are commonly deficient in several micronutrients. Weight loss, although beneficial, may also lead to adverse changes in micronutrient status and body composition. The objective of the study is to assess changes in micronutrient status and body composition in obese individuals after a dietary weight loss program.
SUBJECTS/METHODS: As part of a dietary weight loss trial, enrolling 192 obese patients (body mass index 430 kg/m2) with knee osteoarthritis (450 years of age), vitamin D, ferritin, vitamin B12 and body composition were measured at baseline and after 16 weeks. All followed an 8-week formula weight-loss diet 415-810kcal per day, followed by 8 weeks on a hypo- energetic 1200 kcal per day diet with a combination of normal food and formula products. Statistical analyses were based on paired samples in the completer population.
RESULTS: A total of 175 patients (142 women), 91%, completed the 16-week program and had a body weight loss of 14.0 kg (95% confidence interval: 13.3-14.7; Po0.0001), consisting of 1.8kg (1.3-2.3; Po0.0001) lean body mass (LBM) and 11.0kg (10.4-11.6; Po0.0001) fat mass. Bone mineral content (BMC) did not change (-13.5g; P1⁄40.18), whereas bone mineral density (BMD) increased by 0.004g/cm2 (0.001-0.008g/cm2; P1⁄40.025). Plasma vitamin D and B12 increased by 15.3nmol/l (13.2-17.3; Po0.0001) and 43.7pmol/l (32.1-55.4; Po0.0001), respectively. There was no change in plasma ferritin.
CONCLUSIONS: This intensive program with formula diet resulted in increased BMD and improved vitamin D and B12 levels. Ferritin and BMC were unchanged and loss of LBM was only 13% of the total weight loss. This observational evidence supports use of formula diet-induced weight loss therapy in obese osteoarthritis patients.
Introduction
Obese subjects often show micronutrient deficiencies. The reason for this is complex. Obesity reduces the bioavailability of several vitamins and there may be an alteration in nutrient metabolism. Furthermore, the quality of ingested foods may be poor. Obesity and being overweight represent a rapidly growing threat to the health of populations in an increasing number of countries. Positive energy balance deriving from excessive food intake in relation to energy expenditure is the pathophysiological basis of obesity in most cases. Weight loss is expected to result in a significant reduction in risk of the majority of these comorbid conditions. Weight loss has, however, also been associated with (a potentially harmful) loss of muscle mass and bone in obese individuals.
A variety of weight loss methods are available today, including diet therapy approaches such as low-calorie diets and lower-fat diets, change in physical activity patterns, behavior therapy techniques, pharmacotherapy, surgery and combinations of these techniques. Among these, bariatric surgery is the most effective but it is found to aggravate the insufficient state of several micronutrients. As obesity and micronutrient deficiencies are related to and associated with increased risk of morbidity, one must consider the nutritional value and capacity of weight-loss treatments to secure adequate amounts of nutrients and prevent detrimental effects while losing weight. In the current study, we used a prospective cohort of sedentary obese knee osteoarthritis patients, who completed a weight loss trial to look at the effect of a formula low-energy diet on micronutrient status, that is, vitamin D, vitamin B12, ferritin as well as on body composition. Clinically, osteoarthritis causes painful joints and is a leading cause of impaired mobility in the elderly; most patients with sympto- matic knee osteoarthritis have limitations in function that prevent them from engaging in their usual activities.
Our objective was to assess and evaluate changes in micronutrient status (vitamin D, B12 and ferritin) and body composition in obese knee osteoarthritis patients after 8 weeks of low-energy diet followed by 8 weeks of a hypo-energetic diet, including two formula diet products daily.
Results
Of the 192 participants randomized to the trial, 175 (91%) completed the study (returned for final data collection at week 16). Only participants returning for the final examination are included in these analyses. The baseline characteristics of the cohort are presented in Table 1.
The mean age of the participants (±s.d.) was 62.6±6.3 years. The majority of the participants were women, which is typical for knee osteoarthritis (142 of the 175). The mean weight at baseline was 102.4±14.5 kg, corresponding to a BMI of 37.1±4.4 kg/m2. LBM was 50.6±8.7 kg and fat mass was 46.6±9.2 kg. The mean P- 25-OH-vitamin D3 was 48.9±20.1 nmol/l at baseline with 84 (48%) participants having lower values than 50 nmol/l, which is the limit for insufficiency, a threshold applied by the hospital laboratory. The mean value of B12 at baseline was 293.2±120.1pmol/l; 34 (19.4%) participants had values below the recommended level at 200 pmol/l, a threshold applied by the hospital laboratory. The mean ferritin was 117.1±94.6mg/l with two (1.1%) participants having values lower than the threshold of 12mg/l. The mean parathyroid hormone was 6.4±2.2pmol/l with 55 (31.4%) participants having excessive values, that is, above 6.9pmol/l. The mean BMC was 2780.7±462.5g and the mean BMD was 1.20±0.09 g/m2.
After the first 8 weeks, the participants had lost 12.0 kg (95% confidence interval (CI): 11.4 – 12.5 kg; Po0.0001) and showed statistically significant increases in all three micronutrients (see Appendix I). As illustrated in Figure 1, at week 16 the relative change from baseline in the group of 175 participants was in favor of the intensive weight loss program-having substantial improve- ments in vitamin D (31.3%) and vitamin B12 (14.9%), with a clinically relevant weight loss (13.7%) to a large extent because of loss of fat mass (23.6%) rather than LBM (3.6%). The participants had lost a mean of 14.0 kg (95% CI: 13.3 – 14.7 kg; Po0.0001). The BMI was reduced by 5.1 kg/m2 (95% CI: 4.8 – 5.3 kg/m2; Po0.0001). Sixty-two participants (35.4%) had a BMI o30 kg/m2 at week 16. Table 2 shows the mean P-25-OH-vitamin D3 had increased with 15.3nmol/l (95% CI: 13.2-17.3nmol/l; Po.0001) at week 16 and the number of participants with lower values than 50 nmol/l had fallen to 38 (21.7%). The mean value of vitamin B12 had increased 43.7pmol/l (95% CI: 32.1-55.4pmol/l; Po0.0001); with 21 (12%) participants having values below the recommended level at 200 pmol/l. Our study did not show any changes in mean ferritin, and none of the participants presented ferritin values that were below the normal range at week 16. Parathyroid hormone had decreased with 0.87 pmol/l (95% CI: 0.62 – 1.12; Po0.0001) and the number of participants with values of PTH, which were too high had fallen to 28 (16%). We did not find any change in BMC ( 13.5g (95% CI: 33.3 to 6.2g; P1⁄40.18)). Being aware of that BMC was a secondary outcome (amongst many), we cannot exclude the possibility that this finding may be due to a type-2 error (see Ancillary analyses). Finally, there was a statistically significant decrease in the bone area of 20.5 cm2 (95% CI: 36.6 to 4.5 cm2; P 1⁄4 0.013) and an increase in BMD of 0.004 g/cm2 (95% CI: 0.001 to 0.008 g/cm2; P 1⁄4 0.025).
P Christensen 1,2, EM Bartels 1, BF Riecke 1, H Bliddal 1, AR Leeds 2,3, A Astrup 2, K Winther 4 and R Christensen 1,5
1 The Parker Institute, Copenhagen University Hospital at Frederiksberg, Frederiksberg, Denmark
2 Department of Human Nutrition, Faculty of Life Sciences, University of Copenhagen, Frederiksberg, Denmark
3 University of Surrey and North London Obesity Surgery Service, Whittington and Central Middlesex Hospitals, London, England
4 Department of Clinical Biochemistry, Frederiksberg Hospital, Frederiksberg, Denmark and 5Institute of Sports Science and Clinical Biomechanics, University of Southern Denmark, Odense M, Denmark
European Journal of Clinical Nutrition (2012) 66, 504 – 509; doi:10.1038/ejcn.2011.201; published online 21 December 2011
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