"Weight loss medications and surgery change the physiology of body weight regulation and are the best chance for long-term success.
An increased understanding of the physiology of weight loss and regain will underpin the development of future strategies to support overweight and obese individuals in their efforts to achieve and maintain weight loss." Greenway article below
"Current biologically based interventions comprise:
1- anti-obesity drugs,
2-bariatric surgery and,
3- the most recent development, intermittent intra-abdominal vagal nerve blockade" Ochner article below.
1- Nutritional Ketosis (Bullet Proof Reference)
(The Ketogenic diet for health)
2- Diet Medications (4 new diet medications)
"habituation to rewarding neural dopamine signalling develops with the chronic overconsumption of palatable foods, leading to a perceived reward deficit and compensatory increases in consumption.4" Ochner article below
3- Bariatric Surgery
Only banding surgery is solely a restrictive mechanistic procedure and is being done much less often.
If you look on internet this is how it answers the question. It is an old viewpoint.
I learned a different answer when I took the American Board of Obesity Medicine Exam 12-15
Gastric bypass causes increase in GLP-1 which decreases hunger by ileal brake.
Gastric Sleeve causes decrease in Ghrelin
"Further, gastric bypass corrects obesity-induced changes in appetite-related hormone profiles11 and neural responsivity,12 which might explain why bariatric surgery is the only available treatment to show long-term effectiveness."
Christopher N Ochner, Adam G Tsai, Robert F Kushner, Thomas A Wadden
Published Online: 11 February 2015 article in link below.
Latest Science on Obesity summed up at this link