To the Editor: We read with interest the work presented by Markovic and Natoli, highlighting the importance of recognising the nutrient density of foods in managing overweight and obese patients.1 We present data to support their observation that it should not be assumed that a patient who is overweight or obese has a nutritionally adequate diet.

Our data were obtained as part of the Geelong Osteoporosis Study from an age-stratified sample of men randomly selected from electoral rolls for the Barwon Statistical Division in Victoria. Dietary intake was estimated using a food frequency questionnaire developed by the Cancer Council Victoria.2 Basal metabolic rate (BMR) was estimated from the Schofield equations, based on age and weight. Data were excluded if the ratio of energy intake (EI) (from food and alcohol combined) to BMR was < 0.9. The sample comprised 1175 men aged 20–93 years (median age, 56 years [interquartile range, 39–73 years]; mean weight, 81 kg [SD, 14 kg]; mean height, 1.75 m [SD, 0.07 m]). Participants were grouped by body mass index (BMI) into three categories: normal weight (BMI < 25 kg/m2), overweight (BMI 25.0–29.9 kg/m2) and obese (BMI ≥ 30 kg/m2). Estimates of physical activity were derived from self-report. Written, informed consent was obtained from participants, and the study was approved by the Barwon Health Human Research Ethics Committee.

We investigated the breakdown of macronutrients, vitamins and minerals listed in the “virtual” case report presented by Markovic and Natoli1 and expressed intakes as a percentage of recommended dietary intake (RDI).3,4 Despite adequate EI, the diets of men in all BMI categories were low in zinc, calcium, folate and fibre (Box).

We acknowledge that there are limitations posed by self-reported dietary intakes and physical activity levels. The EI–BMR ratio decreased with increasing BMI (median [interquartile range], 1.4 (1.2–1.7), 1.3 (1.1–1.6) and 1.2 (1.0–1.5) for normal weight, overweight and obese subjects, respectively), suggesting that under-reporting may have been more common with increasing BMI. We also acknowledge that RDIs are not thresholds for dietary deficiencies. Within these constraints, however, these data suggest that where there are nutritional shortcomings in diets, they are not limited to men of normal weight-for-height, but are also apparent among those who are overweight and obese. These shortcomings suggest that nutrient-dense foods, such as whole grains and vegetables (particularly leafy green vegetables) are underconsumed, while processed foods with high saturated fat and salt content are consumed excessively. These observations underscore the importance of recognising the nutrient density of foods so that nutrition is not compromised when EI is restricted.

To the Editor: Markovic and Natoli draw attention to the frequent presence of nutritional deficiencies in obesity.1 While the authors detail various nutrient deficiencies that may arise from a nutrient-poor diet, they do not discuss the possibility of vitamin D deficiency.

Normally the main source of vitamin D is that synthesised in skin exposed to ultraviolet B radiation. A nutrient-rich or nutrient-poor diet alone is unlikely to provide adequate vitamin D unless foods are supplemented with vitamin D. Vitamin D deficiency in obese people is prevalent, and Holick has described an inverse relationship between body mass index and 25-hydroxyvitamin D levels, with sequestration of vitamin D in body fat reducing its availability.2 Vitamin D deficiency is associated with various conditions for which obesity is a risk factor, including cancer, depression, altered glucose metabolism and cardiovascular disease.2

A prospective study would be required to determine whether vitamin D supplementation is able to modify some of these associations. Increasing vitamin D levels are associated with improved muscle strength,2 and thus vitamin D supplements may be of benefit in obese patients with reduced vitamin D levels. Furthermore, combined vitamin D and calcium supplementation may have a small beneficial role in preventing type 2 diabetes.3 Pending more evidence, it would be prudent to consider measuring 25-hydroxyvitamin D levels in obese people and correcting any deficiency. In view of the large amount of adipose tissue in obese people, it is likely that they would require higher than normal doses to achieve repletion of their vitamin D stores.