“And put a knife to thy throat, if thou be a man given to appetite.” Proverbs 23:2

According to worldwide statistics collected in 2015, a total of 107.7 million children and 603.7 million adults were obese. Among the 20 most populous countries, the highest level of adult obesity was observed in Egypt (35.3%) and the highest level of childhood obesity was observed in the United States (12.7%). Although the prevalence of obesity is less in children than adults, the rate of increase in childhood obesity is greater than the increase in adult obesity over the last 25 years. An elevated BMI contributed to 4.0 million deaths which represented 7.1% of deaths from any cause. It also contributed to 120 million disability-adjusted life-years (a figure calculated as the sum of years lived with disability and years of life lost due to high BMI), which represented 4.9% disability-adjusted life-years from any cause among adults globally.

A total of 39% of the deaths and 37% of the disability-adjusted life-years that were related to high BMI occurred in persons with a BMI of less than 30, which is below the level of obesity. Because of this fact, the definition of overweight and obesity remains controversial in relation to risk of disability and disease; research shows that the traditional calculation of Body Mass Index (BMI) is not enough to determine overall risk. Research is now showing that increased rates of sickness, disability and death with increased weight can occur in people whose BMI’s are not yet in the obese range; however, as BMI numbers increase, the risk of death and disability also increases.

The reason that BMI numbers do not always indicate one’s risk or protection from disease is due to the fact that BMI numbers do not reflect the distribution of fat in the body. It is proven that increased waist circumference, or waist to hip ratio is the greatest predictor of disability and death from obesity. For example, in women a BMI <21 (considered underweight) is associated with the greatest protection from death from heart disease. Yet for many women, a BMI near 30 may still not be of concern if the weight is distributed in the pelvis and not the abdomen. Therefore, when assessing an individual’s overall risk, not only should BMI be considered, but how fat is distributed in the body.

We began last month by looking at specific diseases and illnesses that were linked to obesity. These diseases may also occur in individuals who are of normal weight; however, the risk increases with increased weight. This month we will continue to look at another group of diseases that occur in higher numbers in individuals who are obese.

OSTEOARTHRITIS

There are approximately 100 different types of arthritis. The most common is osteoarthritis (OA). Aging is the greatest risk factor for OA; however, OA is not an inevitable consequence of growing old. Changes in the musculoskeletal system when we age increases the risk of OA, but the joints affected and the severity of the disease are more closely related to other OA risk factors, including obesity, genetics, and joint injury. Other risk factors for OA include gout and diabetes, two conditions also related to obesity as a causal factor. Often OA is referred to as the “wear and tear” arthritis.

In normal joints, a firm, rubbery material called cartilage covers the end of each bone. Cartilage provides a smooth, gliding surface for joint motion and acts as a cushion between the bones. It also absorbs energy from the shock of physical movement. Over the years “wear and tear” causes damage to the cartilage and it breaks down, leading to symptoms such as joint pain and stiffness, particularly first thing in the morning or after resting. Affected joints also become swollen. As OA worsens, bones may break down and develop new bone outgrowths, called spurs, to form around the joints. Bone spurs can be associated with pain, numbness, tenderness, and weakness if they are irritating adjacent tissues. Bits of bone and cartilage can also break off and float around the joint.

In advanced cases, there is a total loss of the cartilage cushion between the bones of the joints, causing changes in the shape of the bones. Loss of cartilage cushion causes bone to rub against bone, leading to even more damage, with an

increase in pain and limitation of joint mobility. Over time, the joint loses its normal shape. By the time a person has symptoms from osteoarthritis, it is no longer just a disease of cartilage. Bone has changed, muscles across the joint have often weakened and there is occasionally inflammation in the lining of the joint. Despite the decrease in mobility caused by OA, there is no evidence that the development of OA leads to the onset of obesity. Some doctors also believe your chances of osteoarthritis increase when you are obese because your body’s ability to circulate blood and oxygen decreases.

For every kilogram of weight, the risk of developing osteoarthritis increases by 9–13 per cent. An increase in weight is also associated with pain in all weight-bearing joints. When OA is caused by obesity, the weight-bearing joints are most affected because of the extra pressure from added weight on the joint and the cartilage. Typically the joint that is affected most by obesity is the knee joint, especially with excess upper body weight. Next to aging, obesity is the most significant risk factor for OA of the knees. People with OA experience 30 percent more falls and have a 20 percent greater risk of fractures than people without OA. These risks are higher because of decreased mobility, muscle weakness and impaired balance. Weight loss will decrease the stress on the knees, but sometimes the damage cannot be reversed, and a total knee replacement is needed. There are new therapies available that have the ability to slow the progression of OA in older adults. This will have enormous health implications, given the aging population and in the increase in risk factors such as obesity.

GOUT

Gout is a form of inflammatory arthritis that develops in some people who have high levels of uric acid in the blood. Because of these high uric acid levels, painful gout attacks are caused because uric acid crystals build up around joints. Uric acid can form needle-like crystals in a joint and cause sudden, severe episodes of pain, tenderness, redness, warmth and swelling. There is a very strong connection between excess weight and the risk of developing gout and gout attacks. The more you weigh, the higher your risk, and the more likely you are to have recurrent attacks. This is because the more you weigh the less efficient your body is at removing uric acid. Carrying extra weight slows down the removal of uric acid by the kidneys. Insulin resistance, a state in which insulin levels remain abnormally high because the body has reduced sensitivity to the hormone, is the major player in the increased risk of gout linked to body fat. When people are overweight or obese, their bodies produce more insulin. Higher levels of insulin circulating throughout the body inhibit uric acid elimination by the kidneys. One study found that just gaining 10 pounds over four months was associated with an increased incidence of gout.

The area in which someone carries fat also contributes to gout. Too much visceral (belly) fat is linked to insulin resistance and development of gout. People who were not obese as measured by BMI, but who had high levels of visceral fat, were more likely to have gout than their smaller-bellied counterparts (47.4% versus 27.3%). Gout is not just an arthritis, but also a metabolic disease (metabolism refers to the body’s processes involved in converting food to energy), in which the primary metabolic problem is high uric acid. Like obesity and diabetes, high uric acid is a direct risk factor for cardiovascular disease. Another common misunderstanding about gout is that while attacks may make the condition seem like something that comes and goes, it is a chronic disease. Gout attacks are usually a sign that the body is in an imbalanced metabolic state, which can lead to more serious diseases.

SPINAL CONDITIONS

Your spine is made up of 33 vertebrae, a series of small irregular-shaped bones, having several projections for movement and muscle attachment, and a hole, creating the spinal canal through which the spinal cord passes; the spinal cord is the connection between the brain and the nerves that travel throughout the body. The vertebrae are structured so that they protect the spinal cord and the nerve roots which originate from the spinal cord. These vertebrae are cushioned and separated by rubbery, gel-filled discs that absorb the shock of weight and everyday movement. They prevent the vertebrae from rubbing against each other. A spinal disc has a tough outer wall that protects the disc; the centre of the disc, called the nucleus, has high water content that stores oxygen and nutrients. In order for your spine to function properly, these discs must be well hydrated. As a result of the natural aging process, as well as through overuse or serious injury, the discs begin to lose elasticity over time, making them less able to absorb the stress being placed on them and vulnerable to damage.

The spine or backbone supports much of the body’s weight, and overloading the spinal column can contribute to its degeneration through the years. Obesity is a major factor in the development of neck and back pain for millions of people around the world. Excessive weight can cause stress on all of the spine’s parts, such as the joints, vertebrae and spinal discs, contributing to conditions like degenerative disc disease (DDD), bulging discs, herniated discs and compression fractures in the back. While primarily age-related conditions, being overweight or obese adds to the stress being placed on the spinal discs, which can accelerate their breakdown.

DDD is the weakening of one or more discs between the vertebrae. This condition causes the disc to lose water content and flatten. When this happens, the discs start to lose cushioning and do not absorb the shocks as well, when you are walking, running, or jumping. This deterioration is particularly common in the lumbar (lower) and the neck region of the spine because of the flexibility of these areas, combined with the amount of weight they support. DDD is more common in obese people, speeding up the aging process by adding to the stress placed on the discs. Typically DDD affects people over the age of 60, but it can also be commonly seen in people between the ages of 30–50. In addition to pain in the spinal area, symptoms of DDD include pain inthe legs or arms, muscle spasms, numbness or tingling, stiffness or weakness in muscles, difficulty walking or sitting comfortably.

In a bulging disc, a small portion of the disc protrudes into the spinal canal. No portion of the nucleus has leaked out of the disc. A bulging disc is considered “contained”. This means no tear or rupture is present within the outer layer of the disc. A bulging disc only becomes serious when it bulges enough to cause narrowing of the spinal canal. This may cause the disc to press on a nerve; symptoms will occur in whatever part of the body the affected nerve serves.

A herniated disc is “non-contained”, which means a tear or rupture is present. A portion of the gel-like center of the disc has leaked into the spinal canal. A herniated disc might have begun as a bulging disc, but has created so much pressure on the outer wall of the disc that a rupture occurs. This is more likely to happen in people who have significantly more weight in their upper body that is transferred to the weakened disc. While it is more common to have a bulging disc than a herniated disc, a herniated disc is more likely to be painful. The material that has ruptured into the spinal canal from the nucleus can cause pressure on the nerves in your spinal canal. There is also some evidence that the nucleus material causes a chemical irritation of the nerve roots. Both the pressure on the nerve root and the chemical irritation can lead to problems with how the nerve root functions. The combination of the two can cause pain, weakness, and numbness in the area of your body to which the affected nerve supplies sensation. If the herniation occurs in the thoracic (upper to mid-back) spine, the pressure can also affect the spinal cord. This is due to the fact that there is little extra space within the spinal canal of the thoracic spine. Too much pressure on the spinal cord can lead to paralysis from the waist down.

Compression is a term which means to press down upon forcefully. In this type of injury, it is the actual weight of the body pressing down forcibly upon a joint or bone, enacting enough pressure to actually cause bones to crack under the stress. A compression fracture of the back happens when your vertebrae, or bones of the spine, break. Compression fractures can occur anywhere in the spine, but most commonly in the lower thoracic spine and upper lumbar spine (lower back area). Because the excess weight in this area is more prone to cause pressure to the vertebrae in obese people, compression fractures can become very common. Osteoporosis, which is low bone density, combined with obesity creates an optimal environment for compression breaks to occur.

Stenosis refers to a “narrowing or constricting space.” Spinal stenosis is the narrowing of the spinal canal. Generally, it occurs in two sections of the spine, in the neck (cervical) and lower spine (lumbar). These two sections tend to bend, move and provide flexibility more than the other areas of the spine. When the spinal canal is narrowed, the nerves in the spinal cord are more likely to be compressed if there is continual bending and moving of the vertebrae. There is usually an underlying reason that causes the spinal canal to narrow. Some of these are related to the aging process. Some of these are conditions that we talked about already, including bulging and herniated discs that can be triggered by obesity. Another cause of spinal stenosis is tissue inflammation in one’s back. Because of this inflammation, the canals grow smaller, and the nerve becomes compressed by the inflammation. One of the leading causes of tissue inflammation in the back is obesity. Symptoms of nerve compression caused by spinal stenosis can include pain that travels along a nerve, unexpected muscle weakness, numbness or tingling in fingers or toes, sciatica. In extreme cases, loss of bladder control can occur.

The health of the spine is vital to the proper functioning of the rest of the body. If the connection between the brain and the nerves are affected, loss of function can occur in multiple areas of the body. This often leads to years of disability due to pain, muscle weakness of the arms and legs, and decreased mobility.

As seen in the last two articles, the prevalence and disease burden related to years of disability and years of life lost due to elevated BMI, and especially obesity is significant worldwide. There is increased evidence to suggest that lifestyle choices are impacting not only the developed countries of the world, but the developing countries as well. Changes need to be made at a global level to improve the health of people everywhere. We have not yet covered all the diseases associated with obesity—another reflection of the far-reaching impact that obesity has on one’s health. We will continue to discuss the health risks associated with obesity in part 3 next month.