Although more significant weight loss may result in more benefits to the body, even losing > 2.5 % of weight can improve blood glucose and triglycerides. More considerable reductions ( say >10 %) would lead to improvements in sleep apnea and fatty liver. Significant weight loss ( > 15 kg loss ) can lead to remission of diabetes in many people with shorter disease duration. People who have undergone bariatric surgery and lost significant weight have seen improvements in heart disease and risk of death.
So, if you are a person with obesity and starting a weight loss program, congratulate yourself for every kilogram lost!