Surgery Counteracts Increases in Appetite that Contribute to Weight Regain
By Cynthia K. Buffington, PhD
With traditional weight loss, several different physiological conditions occur that can lead to very rapid weight regain. One of these conditions involves changes in the production of specific gut factors and circulating hormones that regulate the appetite centers of the brain. This will likely cause hunger and an increase in appetite. These changes in appetite regulators persist long term following a diet and are believed to contribute significantly to weight regain1.
Bariatric surgery helps to induce long term weight loss by counteracting the increase in appetite and hunger that occurs with weight reduction. One way bariatric surgery compensates for increases in hunger and appetite with weight loss is by reducing the amount of food the stomach will hold. In addition, bariatric surgery suppresses hunger and the risk of weight regain by altering production of certain gut hormones that regulate appetite and feelings of fullness.
The GI tract produces a number of gut hormones that play a role in appetite regulation. Three of these are produced by specific cells in the lower part of the gut in response to a meal, i.e. peptide YY (PYY), glucagon-like peptide-1 (GLP-1) and oxyntomodulin (OXN)2-3. An increase in these gut hormones following a meal causes feelings of fullness and a reduction in appetite. For the obese, meal-stimulated increases in PYY, GLP-1, and OXN are blunted or may even be negligible. Certain bariatric procedures, however, including the gastric bypass, sleeve gastrectomy and the duodenal switch, lead to exaggerated meal-stimulated increases in these gut hormones, along with satiety and a reduction in hunger and appetite.
Some bariatric procedures also reduce appetite by suppressing ghrelin, the ‘hunger’ hormone 2-3. Ghrelin increases when the stomach is empty or with dietary weight loss. Ghrelin acts upon the appetite centers of the brain to increase hunger and appetite. A primary site for production of ghrelin is the stomach, and removal of a large part of the stomach, such as occurs with the sleeve gastrectomy, results in immediate and long term suppression of ghrelin, along with reduced hunger and appetite. Other surgeries, such as the gastric bypass and duodenal switch may also, at least temporarily, suppress ghrelin.
By favorably affecting production of specific gut hormone and by altering the size of the stomach and/or anatomy of the gut, bariatric surgery counteracts the increase in hunger and appetite that occurs with diet. Such surgery-induced changes in appetite regulation contribute to the long term weight loss success of bariatric surgeries.
1Sumithran P et al. N Engl J Med 2011
2Scott and Batterham. Am J Physiol Regul Integr Comp Physiol 2011
3Suzuki et al. J Obes 2011