A research team led by the London School of Hygiene and Tropical Medicine examined 3,882 records of patients who had undergone weight-loss surgery and a similar group of people who had not undergone the procedure and followed them for up to around 4 years.
They found that weight loss surgery patients underwent rapid weight loss for the first 4 months after surgery at a rate of almost 5 kilos a month. Weight continued to fall off, albeit at a slower rate, up to the end of year 4.
The researchers found that gastric bypass and sleeve gastrectomy were more successful procedures for achieving weight loss than other types of procedure. The estimated average 4 year weight loss was 83.8 lb (38 kg) for gastric bypass, 68.3 lb (31 kg) for sleeve gastrectomy and 44 lb (20 kg) for gastric banding.