Simply put, obesity is the result of taking in more calories through your diet than you are burning through physical activity.
The reasons for this calorie imbalance vary from person to person. It can sometimes be linked to the genes we were born with, or our environments, as well as our individual behaviour and choices. And some drugs and diseases can also contribute to weight gain.
Most people can reach and stay within a healthy weight range by eating healthily, eating smaller amounts and becoming more active. Visit our tips and advice on keeping a healthy weight.
How could obesity lead to cancer?
What is known about the relationship between obesity and cancer?
Which cancers are affected?
Research has shown that many types of cancer are more common in people who are overweight or obese, including cancers of the breast (in women after the menopause), bowel, womb, oesophageal (food pipe), pancreatic, kidney, liver, upper stomach (gastric cardia), gallbladder, ovarian, thyroid, myeloma (a type of blood cancer), and meningioma (a type of brain tumour).
This list includes 2 of the most common types of cancer – breast and bowel cancers - and 3 of the hardest to treat – pancreatic, oesophageal and gallbladder cancers.
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There is consistent evidence that higher amounts of body fat are associated with increased risks of a number of cancers (, including:
There is consistent evidence that higher amounts of body fat are associated with increased risks of a number of cancers (, including:
Endometrial cancer: Obese and overweight women are two to about four times as likely as normal-weight women to develop endometrial cancer (cancer of the lining of the uterus), and extremely obese women are about seven times as likely to develop the more common of the two main types of this cancer The risk of endometrial cancer increases with increasing weight gain in adulthood.
Esophageal adenocarcinoma: People who are overweight or obese are about twice as likely as normal-weight people to develop a type of esophageal cancer called esophageal adenocarcinoma, and people who are extremely obese are more than four times as likely
Gastric cardia cancer: People who are obese are nearly twice as likely as normal-weight people to develop cancer in the upper part of the stomach, that is, the part that is closest to the esophagus
Liver cancer: People who are overweight or obese are up to twice as likely as normal-weight people to develop liver cancer. The association between overweight/obesity and liver cancer is stronger in men than women
Kidney cancer: People who are overweight or obese are nearly twice as likely as normal-weight people to develop renal cell cancer, the most common form of kidney cancer .The association of renal cell cancer with obesity is independent of its association with high blood pressure, a known risk factor for kidney cancer .
Multiple myeloma: Compared with normal-weight individuals, overweight and obese individuals have a slight (10% to 20%) increase in the risk of developing multiple myeloma (
Meningioma: The risk of this slow-growing brain tumor that arises in the membranes surrounding the brain and the spinal cord is increased by about 50% in people who are obese and about 20% in people who are overweight
Pancreatic cancer: People who are overweight or obese are about 1.5 times as likely to develop pancreatic cancer as normal-weight people
Colorectal cancer: People who are obese are slightly (about 30%) more likely to develop colorectal cancer than normal-weight people
A higher BMI is associated with increased risks of colon and rectal cancers in both men and in women, but the increases are higher in men than in women
Gallbladder cancer: Compared with normal-weight people, people who are overweight have a slight (about 20%) increase in risk of gallbladder cancer, and people who are obese have a 60% increase in risk of gallbladder cancer
The risk increase is greater in women than men.
Breast cancer: Many studies have shown that, in postmenopausal women, a higher BMI is associated with a modest increase in risk of breast cancer. For example, a 5-unit increase in BMI is associated with a 12% increase in risk
Breast cancer: Many studies have shown that, in postmenopausal women, a higher BMI is associated with a modest increase in risk of breast cancer. For example, a 5-unit increase in BMI is associated with a 12% increase in risk
Among postmenopausal women, those who are obese have a 20% to 40% increase in risk of developing breast cancer compared with normal-weight women . The higher risks are seen mainly in women who have never used menopausal hormone therapy and for tumors that express hormone receptors. Obesity is also a risk factor for breast cancer in men (23).
How might obesity increase the risk of cancer?
Fat tissue (also called adipose tissue) produces excess amounts of estrogen, high levels of which have been associated with increased risks of breast, endometrial, ovarian, and some other cancers.
Obese people often have increased blood levels of insulin and insulin-like growth factor-1 (IGF-1). (This condition, known as hyperinsulinemia or insulin resistance, precedes the development of type 2 diabetes.) High levels of insulin and IGF-1 may promote the development of colon, kidney, prostate, and endometrial cancers .
Fat cells produce adipokines, hormones that may stimulate or inhibit cell growth. For example, the level of an adipokine called leptin, which seems to promote cell proliferation, in the blood increases with increasing body fat. And another adipokine, adiponectin—which is less abundant in obese people than in those of normal weight—may have antiproliferative effects.
Fat cells may also have direct and indirect effects on other cell growth regulators, including mammalian target of rapamycin (mTOR) and AMP-activated protein kinase.
Other possible mechanisms by which obesity could affect cancer risk include changes in the mechanical properties of the scaffolding that surrounds breast cells and altered immune responses, effects on the nuclear factor kappa beta system, and oxidative stress(
How many cancer cases may be due to obesity?
Dr Vishnubala, a GP in York, talks about how obesity can cause cancer, who is at risk, and how to lose weight.
What is my risk of developing cancer if I'm overweight or obese?
The risk is greater the more weight you gain and the longer you are overweight for. But that doesn’t mean the damage is done. You can help stack the odds against cancer by avoiding gaining more weight. And evidence is growing to show risk can start to go back down with weight loss. Plus the best ways to lose weight for most people are by eating healthily and moving more which on their own reduce cancer risk.
If you are thinking of losing weight and think you need support, a personal trainer,your doctor or nurse will be able to help.
How might obesity increase the risk of cancer?
Fat tissue (also called adipose tissue) produces excess amounts of estrogen, high levels of which have been associated with increased risks of breast, endometrial, ovarian, and some other cancers.
Obese people often have increased blood levels of insulin and insulin-like growth factor-1 (IGF-1). (This condition, known as hyperinsulinemia or insulin resistance, precedes the development of type 2 diabetes.) High levels of insulin and IGF-1 may promote the development of colon, kidney, prostate, and endometrial cancers .
Fat cells produce adipokines, hormones that may stimulate or inhibit cell growth. For example, the level of an adipokine called leptin, which seems to promote cell proliferation, in the blood increases with increasing body fat. And another adipokine, adiponectin—which is less abundant in obese people than in those of normal weight—may have antiproliferative effects.
Fat cells may also have direct and indirect effects on other cell growth regulators, including mammalian target of rapamycin (mTOR) and AMP-activated protein kinase.
Other possible mechanisms by which obesity could affect cancer risk include changes in the mechanical properties of the scaffolding that surrounds breast cells and altered immune responses, effects on the nuclear factor kappa beta system, and oxidative stress(
How many cancer cases may be due to obesity?
How being overweight causes cancer
Extra fat in the body can have harmful effects, like producing hormones and growth factors that affect the way our cells work. This can raise the risk of several diseases, including cancer. More than 1 in 20 cancer cases in the UK are linked to being overweight or obese.
Dr Vishnubala, a GP in York, talks about how obesity can cause cancer, who is at risk, and how to lose weight.
What is my risk of developing cancer if I'm overweight or obese?
The risk is greater the more weight you gain and the longer you are overweight for. But that doesn’t mean the damage is done. You can help stack the odds against cancer by avoiding gaining more weight. And evidence is growing to show risk can start to go back down with weight loss. Plus the best ways to lose weight for most people are by eating healthily and moving more which on their own reduce cancer risk.
If you are thinking of losing weight and think you need support, a personal trainer,your doctor or nurse will be able to help.
Belly fat has harmful effects
When too much fat is carried around the belly, it can do even more damage. So-called ‘apple’ shapes are linked to bowel, kidney, oesophageal, pancreatic, and breast cancers.
It isn’t clear exactly why this is, but it could be to do with how quickly certain chemicals from fat can get into the blood.
A healthy body weight is important for children as well as adults
One in five children are overweight or obese before they begin primary school, and one in three children are overweight or obese by the time they leave.
Obese children are more likely to grow into obese adults, and obese adults are more at risk of cancer. It is possible overweight children may be at increased risk of cancer as adults, regardless of what they grow up to weigh, but the evidence isn’t clear.
By encouraging your children to lead a healthy lifestyle, you can help them keep a healthy body weight as a child as well as later on in life.
SOURCE:CANCER RESEARCH UK
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