Body mass index (BMI) is a calculation that takes a person’s weight and height into account to measure body size.
In adults, obesity is defined as having aBMIof
肥胖is associated with a higher risk for serious diseases, such as type 2 diabetes, heart disease, and cancer.
肥胖is common. The CDC estimates that
But BMI isn’t everything. It has some limitations as a metric.
According to the
Despite these limitations, BMI continues to be widely used as a way to measure body size.
The following
| BMI | Class |
|---|---|
| 18.5 or under | underweight |
| 18.5 to <25.0 | “normal” weight |
| 25.0 to <30.0 | overweight |
| 30.0 to <35.0 | class 1 obesity |
| 35.0 to <40.0 | class 2 obesity |
| 40.0 or over | class 3 obesity (also known asmorbid, extreme, or severe obesity) |
For a doctor to diagnose a child over2 years old or a teenwith obesity, their BMI has to be in the
| Percentile range of BMI | Class |
|---|---|
| >5% | underweight |
| 5% to <85% | “normal” weight |
| 85% to <95% | overweight |
| 95% or over | obesity |
From 2015 to 2016,
Eating more calories than you burnin daily activity and exercise — on a long-term basis — can lead to obesity. Over time, these extra calories add up and cause weight gain.
But it’s not always just about calories in and calories out, or having a sedentary lifestyle. While those are indeed causes of obesity, some causes you can’t control.
Common specific causes of obesityinclude:
- genetics, which can affect how your body processes food into energy and how fat is stored
- growing older, which can lead to less muscle mass and a slower metabolic rate, making it easier to gain weight
- not sleeping enough, which can lead to hormonal changes that make you feel hungrier and crave certain high-calorie foods
- pregnancy, as weight gained during pregnancy may be difficult to lose and might eventually lead to obesity
Certain health conditions can also lead to weight gain, which may lead to obesity. These include:
- polycystic ovary syndrome (PCOS), a condition that causes animbalanceof female reproductive hormones
- Prader-Willi syndrome, a rare condition present at birth that causes excessive hunger
- Cushing syndrome, a condition caused by havinghigh cortisol levels(the stress hormone) in your system
- hypothyroidism(underactive thyroid), a condition in which thethyroid glanddoesn’t produce enough of certain important hormones
- osteoarthritis (OA)and other conditions that cause pain that may lead to reduced activity
A complex mix of factors can increase a person’s risk for obesity.
Genetics
Some people have genes that make it difficult for them to lose weight.
Environment and community
Your environment at home, at school, and in your community can all influence how and what you eat, and how active you are.
You may be at a higher risk for obesity if you:
- live in a neighborhood withlimited healthy food optionsor with
many high-calorie food options, like fast-food restaurants - haven’t yet learned to cook healthy meals
- don’t think you can afford healthier foods
-
haven’t found a good place to play, walk, or exercise in your neighborhood
Psychological and other factors
Depressioncan sometimes lead to weight gain, as some people may turn to food for emotional comfort. Certainantidepressantscan also increase the risk of weight gain.
Quitting smokingis always a good thing, but quitting may lead to weight gain too. In some people, it may lead to
Medications, such assteroidsorbirth control pills, can also raise your risk for weight gain.
BMI is a rough calculation of a person’s weight in relation to their height.
Other more accurate measures ofbody fatand body fat distribution include:
- skinfold thickness tests
- waist-to-hip comparisons
- screening tests, such asultrasounds,CT scans, andMRI scans
Your doctor may also order certain tests to help diagnose obesity-related health risks. These may include:
- blood teststo examinecholesterolandglucoselevels
- liver function tests
- a diabetes screening
- thyroid tests
- heart tests, such as anelectrocardiogram(ECG or EKG)
A measurement ofthe fat around your waistis also a good predictor of your risk for obesity-related diseases.
肥胖can lead to more than simple weight gain.
Having a high ratio of body fat to muscle puts strain on your bones as well as your internal organs. It also increasesinflammationin the body, which is thought to be a risk factor for cancer. Obesity is also amajor risk factorfor type 2 diabetes.
肥胖has been linked toa number of health complications, some of which can be life threatening if not treated:
- type 2 diabetes
- heart disease
- high blood pressure
- certain cancers (breast,colon, andendometrial)
- stroke
- gallbladder disease
- fatty liver disease
- high cholesterol
- sleep apneaand other breathing problems
- arthritis
- infertility
If you have obesity and been unable to lose weight on your own, medical help is available. Start with yourprimary care physician, who may be able to refer you to a weight specialist in your area.
Your doctor may also want to work with you aspart of a teamhelping you lose weight. That team might include adietitian,therapist, or other healthcare staff.
Your doctor will work with you on making needed lifestyle changes. Sometimes, they may recommend medications or weight loss surgery as well.Learn more about treatment for obesity.
Your healthcare team can educate you on food choices and help developa healthy eating planthat works for you.
A structured exercise program andincreased daily activity— up to 300 minutes a week — will help build up your strength,endurance, and metabolism.
Counseling orsupport groupsmay also identify unhealthy triggers and help you cope with any anxiety, depression, oremotional eating issues.
Lifestyle and behavioral changes are the preferred weight loss methods for children, unless they’re extremely overweight.
Your doctor may also prescribe certain prescription weight loss medications in addition to eating and exercise plans.
药物通常prescribed only if other methods of weight loss haven’t worked and if you have a BMI of 27.0 or more in addition to obesity-related health issues.
Prescription weight loss medications either prevent the absorption of fat or suppress appetite. The following are approved for long-term use (at least 12 weeks) by the Food and Drug Administration (FDA):
- phentermine/topiramate(Qsymia)
- naltrexone/bupropion(Contrave)
- liraglutide (Saxenda)
- orlistat (Alli, Xenical), the only one that’s FDA-approved for use in children 12 years old and older
These drugs can have unpleasant side effects. For example, orlistat can lead to oily and frequent bowel movements, bowel urgency, and gas.
Your doctor will monitor you closely while you’re taking these medications.
Weight loss surgery is commonly called bariatric surgery.
This type of surgery works by limiting how much food you can comfortably eat or by preventing your body from absorbing food and calories. Sometimes it can do both.
Weight loss surgery isn’t a quick fix. It’s a major surgery and can have serious risks. Afterward, people who undergo surgery will need to change how they eat and how much they eat, or they risk getting sick.
However, nonsurgical options aren’t always effective at helping people with obesity lose weight and reduce their risk for comorbidities.
Types of weight loss surgery include:
- Gastric bypass surgery.In thisprocedure, your surgeon creates a small pouch at the top of your stomach that connects directly to your small intestine. Food and liquids go through the pouch and into the intestine, bypassing most of the stomach. It’s also known as Roux-en-Y gastric bypass (RYGB) surgery.
- Laparoscopic adjustable gastric banding (LAGB).LAGB separates your stomach into two pouches using a band.
- Gastric sleeve surgery.Thisprocedureremoves part of your stomach.
- 与十二指肠胆胰分流开关。This procedure removes most of your stomach.
Candidates for surgery
For decades, experts recommended that adult candidates for weight loss surgery have a BMI of at least 35.0 (classes 2 and 3).
However, in 2018 guidelines, theAmerican Society for Metabolic and Bariatric Surgery (ASMBS)endorsed weight loss surgery for adults with BMIs of 30.0 up to 35.0 (class 1) who:
- have related comorbidities, especially type 2 diabetes
- haven’t seen sustained results from nonsurgical treatments, such as eating and lifestyle modifications
For individuals with class 1 obesity, surgery is most effective for those between the ages of 18 and 65 years old.
People will often have to lose some weight before undergoing surgery. Additionally, they’ll normally undergo counseling to ensure that they’re both emotionally prepared for the surgery and willing to make the necessary lifestyle changes that it’ll require.
Only a few surgical centers in the United States perform these types of procedures on children under 18 years old.
There’s been a dramatic increase in obesity and in obesity-related diseases in the last couple decades. This is the reason why communities, states, and the federal government are putting an emphasis on healthierfood choicesandactivitiesto help turn the tide on obesity.
On a personal level, you can helpprevent weight gain and obesity通过健康的生活方式选择:
- Aim for moderate exerciselikewalking,swimming, orbikingfor 20 to 30 minutes every day.
- Eat wellby choosing nutritious foods, likefruits,vegetables,whole grains, andlean protein.
- Eat high-fat, high-calorie foods in moderation.
