I've just read Your Cat by Elizabeth Hodgkins who is an American vet who specialised in treating cats before she retired, particularly seriously overweight and/or diabetic cats. She's not advocating raw food, although she says it's good for cats, but she is advocating wet food.
Her reasoning is that the majority of dry food is made predominantly of carbohydrate, plant sources coated in fat and flavour to make it palatable to cats. But cats' natural diet is protein and fat from killed animals, with very little plant material or other carbs, and dry food doesn't replicate it at all. She says that wet food is much more suitable for cats and replicates their natural diet better.
She gives multiple case studies throughout the book of overweight and/or diabetic cats who were fed predominantly on dry food, including "diet" or "light" food. She reports that switching the cats to wet food facilitated much better weight loss and in most cases, got their diabetes under control so well the cats no longer needed insulin, and when they did still need it, their blood sugars were more stable and they needed lower doses.
I've lent the book to a friend so I can't give more detail, but it's worth a read if you're interested in cat diets. It's convinced me to switch Pete from dry breakfasts and wet dinners to two wet meals with a small amount of high protein dry food in his activity feeder.
It's also worth looking at the calorie and nutritional content of dry food compared to wet. I emailed Iams, Purina, Pets at Home and Go Cat about the calorie content of their food (which isn't on the packaging) and even the diet stuff is over 300 kcal per 100g, with protein content of under 30% for most of them. On the other hand, Thrive 90% chicken dry food is 186 kcal per 100g and has a protein content of over 80%. The wet foods I've investigated - Felix, Kitekat, Iams, Whiskas and Tesco - are all between 70-95 kcal per 100g pouch, with well over 80% protein.
As far as raw food goes, she says that many people worry about food poisoning for cats who eat raw diets, but she points out that cats who would otherwise be killing live prey and eating it, perhaps caching a large kill and eating it over several days, are unlikely to get food poisoning from meat.
The book made sense to me, and I'm comfortable that a wet food diet with a small amount of dry is the right thing for Pete. I've also scrapped the Dreamies after I saw him gagging on the dryness of one but still desperately trying to eat it, and his treats now are Thrive freeze-dried meat and fish pieces.