London: A UK-based Indian-origin doctor, who has been championing an anti-obesity drive as a means to combat the severe effects of COVID-19, on Thursday released a new book that offers a “simple, evidence-based" plan to help improve health parameters.Dr Aseem Malhotra’s ‘The 21-Day Immunity Plan: How to Rapidly Improve Your Metabolic Health and Resilience to Fight Infection’ is pegged as a tried and tested method of how in just 21 days people can prevent, improve and even potentially reverse many of the underlying risk factors that exacerbate how infections, including coronavirus, affect humans and improve their ability to recover.“Poor metabolic health equals poor immune health.