(CNN) Do you have pounds to lose but don't have a weight loss plan? If you are seriously considering how to go about shedding pounds, there are three proven levels of intervention, depending on your individual needs.
Intervention 1: Lifestyle changes
If you are severely overweight and have not been able to lose an adequate amount of weight with lifestyle changes or weight loss medications, or if you have serious health issues related to obesity, bariatric (or weight loss) surgery is a potential option.
"You consider surgery when other therapies for obesity fail," said Sue Cummings, a registered dietitian who was clinical programs coordinator at the Massachusetts General Hospital Weight Center for the past 20 years. "The person has been through everything -- and now they have diabetes, hypertension, sleep apnea, arthritis. ... That's when you would really start to think about surgery."
Weight loss surgeries performed in the US include gastric bypass, sleeve gastrectomy (also known as gastric sleeve) and a procedure called biliopancreatic diversion with duodenal switch. The latter has the best outcomes in terms of weight loss and remission of many medical conditions associated with obesity, according to Cummings. However, it also carries the most risks.
The adjustable gastric band is another option, though long-term risks associated with the band have led to a significant decrease in surgeons performing the procedure, Cummings said.
The criteria for bariatric surgery include a body mass index (BMI) of 40 or higher (or more than 100 pounds overweight) or a BMI of 35 or higher with health problems including type 2 diabetes, high blood pressure, heart disease or sleep apnea. (A BMI of 30 or more with a serious health problem is indicated only for the gastric band).
The surgeries result in weight loss for two reasons: They reduce the amount of food one can eat, and they cause changes in hormones produced in the intestines that help reduce hunger, increase fullness and regulate blood sugar. For a detailed description of how the different weight loss surgeries work, check the American Society for Metabolic and Bariatric Surgery's online guide.
In essence, the reason most bariatric surgeries are so effective in producing long-term weight loss is that they strongly affect the physiological regulation of body weight, interfering with signals that defend against starvation and weight loss, Cummings explained. This ultimately changes a person's set point, or the level at which weight tends to stabilize.
"Surgery literally changes how your body regulates body weight," she said.
For example, the fundus, or upper part of the stomach, is the main site where ghrelin, a hormone that stimulates appetite, is produced. After the removal of the fundus in the gastric sleeve, the production of ghrelin is significantly reduced. In the gastric bypass and to a lesser extent the sleeve, there is an accelerated delivery of nutrients into the portion of the small intestine known as the hindgut, which causes an increase in secretion of hormones that inhibit appetite and induce satiety, according to Cummings.
An individual's response to weight loss surgery varies, although on average, people who have bariatric surgery lose 15% to 35% of their starting weight. Gastric bypass tends to result in more weight loss than the band or gastric sleeve, Cummings said, though "every bariatric procedure studied demonstrates similar wide variations in outcomes among patients."
As a consequence of weight loss, bariatric surgery can improve many health conditions related to obesity, including type 2 diabetes, sleep apnea, high blood pressure, high cholesterol levels, acid reflux and joint pain. In gastric bypass, improvement in diabetes occurs within days of surgery and is independent of weight loss. The reason is due to hormonal changes, which enhance insulin's response to nutrients, Cummings explained.
The benefits of weight loss surgery do not come without risks and long-term considerations, however. "About 10% to 20% of patients fail to lose a significant amount of weight, and others experience significant or premature weight regain," Cummings said.
Complications of surgery may include infection, bleeding, poor absorption of nutrients or dehydration early on, as well as ulcers and hernias. A side effect of gastric bypass known as "dumping syndrome" can occur shortly after eating and may result in nausea, dizziness, weakness, cold sweats, cramps and diarrhea.
Long-term outcomes vary, as well. According to one 12-year study of people who had gastric band surgery, one in three experienced band erosion, and nearly half of patients needed to have their bands removed.
It's important to recognize that lifestyle changes after surgery are extremely important. That includes avoiding many food temptations that surround you, such as fast food french fries and the scones at the local coffee shop.
"Surgery is not going to change the environment; therefore, combining lifestyle changes with surgery will produce the best outcomes," Cummings said. Those changes include eating more whole foods, avoiding refined and processed foods, and increasing physical activity each day.
Additionally, lifelong supplementation of vitamins and minerals -- including iron, calcium, folate, vitamins B12 and B1 and vitamin D -- is required. "The risk of deficiencies increase as a patient progresses from surgery, so all patients need to have their nutritional labs monitored yearly for life," Cummings said.
The decision to have weight loss surgery is not an easy one. Every patient needs to be fully informed of the risks and the benefits, and should be evaluated by a multidisciplinary team including a surgeon, a doctor (their primary care physician and/or an obesity medicine specialist), a registered dietitian and a mental health professional, Cummings explained.
Additionally, a full benefit-risk analysis should be performed.
"Do the benefits outweigh the risks? If so, surgery is the most effective therapy," Cummings said, adding that "data show an increased life expectancy due to the remission and/or resolution of over 190 medical conditions associated with obesity, such as type 2 diabetes, heart disease, sleep apnea, high blood pressure, kidney failure and more."