Obesity is a condition of abnormal or excessive fat accumulation in adipose tissue. A body mass index (BMI) over 25 is considered overweight, and over 30 is obese.
The issue has grown to epidemic proportions, with over 4 million people dying each year as a result of being overweight or obese in 2017 according to the global burden of disease (GBD).
Some numbers… (3)
- Worldwide obesity has nearly tripled since 1975.
- 39% of adults aged 18 years and over were overweight in 2016, and 13% were obese.
- Most of the world’s population live in countries where overweight and obesity kills more people than underweight.
- Obesity is preventable.
Overweight children are more prone to becoming overweight adults, especially at higher BMIs (body mass index) or if they have an obese parent (4).
Almost half of overweight adults were overweight as children (4).
What causes obesity? (3)
The fundamental cause of obesity and overweight is an energy imbalance between calories consumed and calories expended.
- an increased intake of energy-dense foods that are high in fat and sugars.
- an increase in physical inactivity.
Adipose (fat) tissue mass increases in two ways: (6)
1. Fat cell hypertrophy: Existing adipocytes enlarge or fill with fat
2. Fat cell hyperplasia: Total adipocyte number increases
The process of weight gain seems to be different in adults and in children (5).
Adults who gain or lose weight may do so through changes in the size of the fat cells (a process known as hypertrophy) . Children, on the other hand, may put on extra fat by increasing the overall number of these cells in the body (a process known as hyperplasia). This may mean that people who got fat during childhood may find it more difficult to shift the weight later in life, compared to those who piled on the pounds as adults.
The average number of fat cells (adipocytes ) rises until the age of about 20, and then remains relatively constant.
An average-sized person has between 25 and 30 billion adipocytes (fat cells), whereas the obese may have more than three to five times this number, particularly when obesity occurs in childhood or adolescence (6).
In adults, the major change in adipose cellularity in weight loss is shrinkage of adipocytes with no change in cell number.
Obesity and Pain (2)
The prevalence of pain is 33% in obesity people. It seems that people with obesity are more pain sensitive, due to a lower pain threshold and pain tolerance. Let’s have a look at several potential mechanisms that may link the two phenomena.
Mechanisms of obesity-related pain
Direct contribution of weight
- Excess weight on weight-bearing joints and skeletal muscle tissue causes tissue and joint damage
Indirect contribution of weight
- The compression forces on the lumbar spine during the lifting tasks is greater in people with obesity compared to people with normal weight.
- Sleep disturbance can increase pain
- Low physical activity levels are associated with low-back pain in a population with obesity
People with overweight and obesity demonstrate significantly lower pain threshold and pain tolerance compared with non-obese controls.
Degree of overweight is associated with higher pain sensitivity.
- Obesity is a low-grade inflammatory disease. Pro-inflammatory immune cells and adipocytes (fat cells) secrete pro-inflammatory proteins (cytokines).
Factors influencing pain sensation
- Women seem to have higher pain prevalence and higher pain sensitivity compared with men
Body fat distribution
- Body regions with more excess body fat (e.g., abdominal area) may also have a higher level of inflammation. Therefore, they are more pain sensitive compared to body regions with less body fat (e.g., hands and forehead).
- The prevalence of vitamin D deficiency is higher among people with obesity.
- Greater osteoarthritis pain ratings were reported in people with vitamin D deficiency in both obese and non-obese groups.
- An animal study suggested that lower diet quality increased pain sensitivity and susceptibility to chronic pain.
Take home message
It is crucial to keep undercontrol your weight in your youth. Obesity is preventable.
Obesity seems to lead to PAIN, despite the interrelationships between Pain and Obesity is complex and still in its infancy.
It is important that you tackle this pathology. Dietary changes, increased physical activity and behavior changes can help you lose weight.
- The association between chronic pain and obesity, 2015;
- Obesity and pain: a systematic review, 2019;
- Obesity, WHO;
- Childhood obesity and adult morbidities, 2010 – The American Journal of Clinical Nutrition;
- Fat cell numbers stay constant through adult life, Nature – 2008;
- Exercise Physiology: Nutrition, Energy and Human Performance, William D. McArdle, 2009.