A very small proportion of obesity is secondary to hypothyroidism which isn’t supplemented with synthroid/thyroid hormone, hypothalamic/pituitary axis dysfunction, adrenal corticotroph, or exogenous corticosteroids. If viruses are blamed its going to be pseudoscience to sell pills.
An accepted rule of nutrition/diet/physiology is that an excess of 3,500 calories will lead to a gain of 1lb of fat.
The basal metabolic rate for an adult in the United States is 1,731 calories (numbers based on averages returned in google, 38.1 years old, 5’11, 181 lbs).
So 1,731 calories for a sedentary person is really easy to surpass. If they surpass that by a few hundred calories a day then they’ll gain a pound every 10 days(ish). After ballooning up they can jump on the ozempic train and lose weight. Or just stay obese.
If you don’t know anyone on ozempic then I’ll share - the weight loss appears mostly due to discomfort. Eating what they used to do becomes very uncomfortable due to abdominal pain/nausea and constipation. So they calorie restrict and they start to lose weight because they’re below their BMR.