CDC stats indicate that the best outcomes for people who contract Covid are those with a BMI of about 25 (give or take) and the worst with BMIs in the obese range. This doesn't mean it is the most significant factor by any means. It also states nothing about the relationship about BMI and age - and you can guess that one.
Overall your proposal doesn't seem to have a lot of contained logic. Should people who develop covid but put on crash diet? It seems like another attempt to deny the seriousness of the outbreak and to promote quackery. Now where's mu Lysol? Time for a drink!
The logic is clear to me. A BMI >25 is considered overweight and >30 is obese. You agree that COVID outcomes are worst for obese individuals. Therefore, it would be logical that overweight individual are also likely to be at higher risk than a "normal" weight individual? While weight or BMI is not the only or most significant factor, it is a good surrogate for numerous health based factors, which are also associated with increased age. So there is no quackery involved, just a possible inability to follow logic.
Excess weight is a very good indicator of metabolic health and the condition of the immune system. I do not have figures for Canada, but in the US, only 12% of the population is considered to be metabolically healthy (based on an assessment of BMI, insulin resistance, CRP, blood sugar, HDL/triglyceride ratio) and I am sure Canadians are not too far behind. This is why comorbidities such as obesity, diabetes and metabolic syndrome along with age are the most significant factors in severity of COVID outcome, as clearly establish by numerous research papers. Suggesting crash diets when someone gets infected is like slamming the stable doors shut after the horse has bolted. However, promoting and improving peoples health by reducing obesity, diabetes, inflammation etc and normalizing hormone, vitamin and mineral levels (particularly Mg, Vitamin D and Zn) prior to infection would have a profound beneficial impact on the heath care system and not just in a reduction in COVID severity.
I have been vaccinated, strongly believe that it is the most effective and speedy way of achieving herd immunity, but I would never support mandatory vaccination.