BMI and Covid Hosptalisations

I keep reading people saying that an alternative to covid vaccinations and social distancing methods are healthy eating and  exercise to reduce BMI. How much would these actually help?

According to the CDC not that much. Body Mass Index and Risk for COVID-19–Related Hospitalization. Graphs here the effect of obesity is greater in those under 65. But even then it seems to be about 20%

Which is not a huge amount. Vaccines reduce hospitalization rates by over 80%. And that is if diets actually could reduce your BMI from obese to recommended levels.