Nutrition research ain’t perfect, but there is a clear relationship between overweight/obesity and hyperuricemia/gout. And you are correct: weight loss can precipitate attacks, but that doesn’t invalidate the role of a healthy diet in limiting gout long term.
To be clear, the meds you mention work great, and anyone with gout should seek a medical professional to treat them. I just wanted to push back a bit at the mentality managing illness just involves “taking something”, rather than addressing modifiable lifestyle choices contributing to gout and other diseases of affluence. That sentiment isn’t directed at you specifically, more a commentary on the evolution of Western medicine.
As for your brother, doing everything “right” doesn’t guarantee freedom from disease. We can’t outrun our genetics. Tophaceous gout is bad, but there are many effective therapies available, including more contemporary meds than colchicine. I don’t know the whole story, but it’s a little concerning his doctor didn’t talk to him about urate-lowering therapy like allopurinol, as it is strongly recommended for those with frequent flares and multiple tophi.
Here are the most recent treatment guidelines, including lifestyle modifications, fwiw.