Kitty is 12 and round, need help

Kitty is 12 now, Shih Tzu, and she has gained almost 2 kg in the last 6 months. Vet says she needs to lose some weight for her joints. We live in a small place in Bang Sue, so she can't really run much around the condo. I've switched her to the lower-calorie food and cut the treats in half. She still begs at the dinner table every single night, and honestly it's hard to say no to that face. Last week my wife gave her a piece of chicken and I only found out later. We take her on short walks along the canal in the evenings, slow pace. She's not thrilled but she does it. Hoping to hear what worked for other people with older dogs.