Nutritional implications of obesity and dieting

Overweight and obese people appear to be at greater risk of suboptimal vitamin and mineral status compared with people of a healthy weight. Nutrients most affected include vitamin D, vitamin B₁₂, carotenoids, folate, vitamin C and iron. The reasons are unknown but may be caused by poor diets, increased requirements or obesity-related changes to nutrient absorption, excretion or metabolism, or a combination of these. Sequestration of fat-soluble vitamins by adipose tissues is also a major factor. Although dietary assessment in obese populations is hampered by under-reporting, there is evidence that dietary patterns characterised by energy-dense, processed foods are more common in groups with a higher body mass index. Dieting practices, bariatric surgery and the use of anti-obesity drugs may compound the risk of nutrient inadequacy, although sustained weight loss helps to improve vitamin D status. A poor nutrient status could accentuate the risk of chronic diseases already experienced by overweight people on account of their excessive fat mass. There is evidence that the use of dietary supplements can improve nutrient status and have a favourable impact on disease risk markers such as lipid profiles and insulin resistance. Whether currently dieting or not, overweight people may benefit from safeguarding vitamin and mineral adequacy by taking a multi-nutrient supplement alongside an increased intake of nutrient-rich foods.