Answer C. Decreased bone mineral density
Constipation is the most frequently reported adverse effect of ketogenic diets. Hyperlipidemia is also commonly reported and may normalize over the first year of treatment. Other commonly reported adverse effects include weight loss, growth problems in children, nausea and vomiting, behavior problems and irritability, lethargy, hypercalciuria, increased liver enzymes, renal stones, diarrhea, and hypoglycemia. There have only been a few reports of loss of bone mineral density in children who followed the ketogenic diet, and reports in adults suggest no loss of bone mineral density over long-term follow-up.
Source: Schoeler NE, Cross JH. Ketogenic dietary therapies in adults with epilepsy: a practical guide. Pract Neurol. 2016;16:208-14.