Under normal conditions, energy intake is roughly equal to energy expenditure, keeping our weight relatively constant. It is often easier to gain weight than to lose it because our body is more sensitive to energy deficits than to surpluses. Due to our biological predisposition and the abundance of food, severe obesity has increased, leading to major health problems. Bariatric surgery is an effective way to achieve long-term weight loss, but the exact mechanisms are not yet fully understood. In addition, complications can arise after surgery. Electrical stimulation of the vagus nerve is also used in the treatment of obesity, although since its FDA approval in 2015, only a small number of patients have been treated with it.
This dissertation of Warner Hoornenborg describes three different procedures: the Roux-en-Y gastric bypass, ileal transposition, and electrical stimulation of the vagus nerve.
We found that weight loss after a Roux-en-Y gastric bypass was mainly caused by reduced energy intake and by the weight of the rats before surgery. Additionally, rats on a high-fat wit added sugar diet experienced less disruption in their daily activity and body temperature immediately after surgery than those on a low-fat diet. Although this seems beneficial, it was also found that this diet led to higher glucose levels after meals due to reduced insulin release.
In rats that underwent ileal transposition, weight loss was also observed, partly because digestion required more energy, but also because there was a temporary reduction in energy intake.
Lastly, we studied electrical stimulation of the vagus nerve. This did not lead to weight loss or improvements in blood sugar regulation in rats with type 2 diabetes. However, in healthy rats, it did result in faster glucose processing. This could potentially be used in the future for the prevention of type 2 diabetes.
