Obesity and Circulating Levels of Vitamin D before and after Weight Loss Induced by a Very Low-Calorie Ketogenic Diet

Background: Vitamin D plays a pivotal role in calcium and phosphorus metabolism, also influencing bone tissue. Several studies have reported that vitamin D blood levels were significantly lower in people with obesity, probably due to its uptake by the adipose tissue. Clinical studies that investigated the changes of circulating levels of vitamin D following weight loss reported controversial data. A very low-calorie ketogenic diet is acknowledged as a reliable treatment to achieve a rapid weight loss. Therefore, we investigated the effect of weight loss, consequent to a very low-calorie ketogenic diet, on vitamin D blood concentrations. Methods: A cohort of 31 people with obesity underwent a very low-calorie ketogenic diet for 10-12 weeks. The serum concentrations of vitamin D, parathormone, calcium and phosphorous were measured before and after weight loss; they were compared to a control group of 20 non-obese, non-diabetic, age- and gender-matched persons. Results: Patients with obesity had a higher habitual intake of vitamin D than the control group (p < 0.05). However, the vitamin D blood levels of the obese group were significantly lower than those of the control group (p < 0.005) and they increased after weight loss (p < 0.001). At baseline, vitamin D blood concentrations of the persons with obesity were significantly correlated with both fat mass-kg (r = -0.40; p < 0.05) and body mass index (r = -0.47; p < 0.01). Following very low-calorie ketogenic diet, the change in vitamin D serum concentrations was correlated only with the change in fat mass-kg (r = -0.43; p < 0.01). Conclusion: This study confirmed that patients with obesity have lower vitamin D levels that normalize after significant weight loss, supporting the hypothesis that vitamin D is stored in the adipose tissue and released following weight loss

Resting energy expenditure and substrate oxidation in malnourished patients with type 1 glycogenosis

Context. Type 1a and 1b glycogenosis (GSD1a, GSD1b) are rare diseases generally associated with malnutrition. Although abnormal substrate oxidation rates and/or elevated energy expenditures might contribute to malnutrition, this issue has not been investigated. Objective. To investigate whether abnormal resting energy expenditure and substrate oxidation rate characterize patients with GSD1. Design. Cross-sectional study. Setting. Outpatient referral center for rare diseases and laboratory of clinical nutrition at the university hospital of Palermo (Italy). Patients. Five consecutive patients with GSD1 (4 type a, 1 type b), 3 males/2 females, age range 19-49 years. Main Outcome Measures. In the context of usual clinical procedures for patients with malnutrition, resting energy expenditure (REE, indirect calorimetry), basal substrate oxidation rate (indirect calorimetry), body composition (bioimpedance method), muscle strength (hand-grip test) and usual laboratory tests were performed. Results. Malnutrition was clearly diagnosed in 2 patients (1 GSD1a and 1 GSD1b), and REE was elevated in all 5 patients but in particular in the 2 malnourished patients (+124% and +32.1% versus predictive values according to Harris-Benedict equations). The 2 malnourished patients also exhibited lower basal protein oxidation rates (7.7% and 6.6%) than the non-malnourished patients (range: 12.1-24.7%), with higher carbohydrate or lipid oxidation rates. Additionally, the 2 patients with malnutrition exhibited higher blood concentrations of lactic acid than the non-malnourished patients. Conclusions. According to data obtained in this small sample of patients with GSD1, an elevated REE seems to be a common characteristic that may contribute to malnutrition. A low basal protein oxidation rate and elevated blood lactic acid concentrations appear to be associated with malnutrition. Type 1 glycogenosis are rare diseases associated with malnutrition. The measured resting energy expenditure was elevated in 5 patients and contributed to explain the occurrence of malnutrition.