Obesity, Diabetes & Heart Diseases: What’s The Link?

Learn what links obesity to diabetes and heart diseases and what preventative measures we can do to avoid these illnesses.

by Samantha Poh

Obesity is perhaps the most prevalent and exacerbating, yet trivialized epidemic that affects all parts of the world. Notably, more than 330 million people in the United States of America (US) are obese, exceeding one-third of their current adult population. In Singapore, Malaysia, and Australia, obesity rates today stand at 6.1%, 15.6%, and 29.0% respectively, and have showed a steadily increasing trend over the past decade.

Apart from being inherently deleterious, obesity has proven to be a major risk factor for type 2 diabetes, heart disease, stroke, dementia, high blood pressure, high cholesterol, osteoarthritis, liver disease, kidney disease, and some types of cancer. Research has found strong linkages and even causative relations between obesity and diabetes, as well as obesity and heart disease. For example, a recent study in the US has shown that obesity accounts for up to 53% of new cases of diabetes, while another study has shown that people with obesity have twice the chance of having a heart failure.

So how does obesity increase our risk for such deadly diseases? And how can we take steps to avoid obesity and its dangerous implications? 

“Overweight” or “Obese”?

“Overweight” and “obesity” both refer to the condition of having excessive and unhealthy fat accumulation in the body due to an energy imbalance, often when a greater amount of calories is consumed than expended. However, the two terms are different as “obesity” is used to describe a higher degree of fat accumulation than “overweight”.

Generally, this differentiation is conducted through the measurement of your body mass index (BMI), which uses your height and weight to estimate your body fat and rate your risk of weight-related diseases. An overweight adult is defined as having a BMI of 25 to 29.9 kg/m2, while an obese adult has a BMI greater than 30 kg/m2. A BMI over 40 kg/m2 is referred to as “morbid obesity”. You can take a simple and quick measurement of your BMI with an online calculator.

However, using BMI to determine whether you are overweight or obese is not a definitive way as it does not guarantee an accurate estimation of your body fat content and localization. On top of a BMI measurement, doctors will employ other indexes and tests with higher accuracy in determining whether one is overweight or obese. These methods, which vary in accuracy and suitability for various special cases (e.g. pregnant women), include:

  • Body fat percentage
  • Waist circumference (WC) 
  • Waist-to-hip ratio (WHR) 
  • Skinfold thickness
  • Underwater weighing (densitometry)
  • Air-displacement plethysmography
  • Dilution method (hydrometry)
  • Bioelectric impedance (BIA)
  • Computerized tomography (CT)
  • Magnetic resonance imaging (MRI)
  • Dual energy X-ray absorptiometry (DEXA)

If you are overweight, the doctor will recommend some lifestyle changes to reduce your chances of becoming obese. If you are diagnosed with obesity, you are at significantly higher risk of having obesity-associated diseases, such as type 2 diabetes mellitus and various heart diseases, and should immediately take steps to reduce body fat. 

The Link Between Obesity & Diabetes

Diabetes is a condition where the body is unable to regulate blood glucose due to impaired insulin production or insulin resistance, evidently observed as a spike in blood glucose (hyperglycemia) after a meal. There are two types of diabetes

1. Type 1 diabetes

Occurs when the pancreas produces little to no insulin. This relatively rare condition, which makes up less than 10% of all cases of diabetes, is not caused by obesity and is solely due to genetic defects

2. Type 2 diabetes

This accounts for more than 90% of all diabetes cases and develops due to diet and lifestyle factors. Ultimately, the pancreas is no longer able to produce enough insulin or the body becomes insensitive to insulin, and is therefore not able to effectively regulate blood glucose. Obesity increases the risk of type 2 diabetes.

Studies have shown that obese individuals are up to 80 times more likely to develop type 2 diabetes than people with a BMI within the normal range (18.5–24.9 kg/kg/m2). Although clear mechanisms have yet to be established, ongoing research has revealed a few possible ways for obesity to cause type 2 diabetes.

Inflammatory response to excessive nutrients

The excessive intake of food in obese individuals means that there is constant and prolonged exposure of cells to too much glucose, free fatty acids, and other nutrients, which damages cells. These cellular injuries, such as mitochondrial dysfunction, fatty acid accumulation, and endoplasmic reticulum stress, induces inflammation that damages insulin-sensitive storage tissues, namely the liver, skeletal muscle, and adipose (fat) tissues. Excessive nutrients in the blood and inflammation also places stress on the insulin-producing β(beta)-cells in the pancreas, causing them to deteriorate. As a result, insulin-sensitive tissues are no longer able to respond to insulin signaling and insulin production is impaired, resulting in type 2 diabetes.

Additionally, parts of the brain that control energy homeostasis (regulation) and insulin action can also be adversely affected by the inflammation brought about by nutrient excess. This results in impaired neuronal mechanisms in the regulation of blood glucose, contributing to type 2 diabetes pathogenesis.

Adipocyte signaling dysregulation

Adipose tissues, also known as adipocytes or fat cells, produce a myriad of signaling molecules known as adipokines. These adipokines travel between cells and organs to induce metabolic changes that regulate the amount of nutrients to be used, stored, or released in different parts of our body. Some inflammatory adipokines, including tumor necrosis factor-α, resistin, and retinol-binding protein 4, are present in higher levels in response to obesity and contribute to insulin resistance. Other adipokines, mainly adiponectin, and display reduced levels in obese states. Adiponectin is an important molecule that has anti-inflammatory effects and functions as an insulin sensitizer, meaning that it increases the sensitivity of storage tissues to insulin. 

Hence, due to obesity, the increase in inflammatory adipokines means that insulin resistance is promoted, while the decrease of adiponectin means that protection against the development of type 2 diabetes is lost.

Ectopic fat deposition

Ectopic, or abnormal, fat deposition in other tissues, such as the skeletal muscle, liver, heart, pancreas, and bloodstream, instead of subcutaneous adipose tissue (fat cells under the skin) can disrupt the normal function of those tissues. Ectopic fat deposition is usually observed in obese individuals due to the excess amount of fat in their body. Large amounts of fat deposition in the liver and muscles, also known as visceral fat, disrupts the insulin sensitivity of these organs and can cause type 2 diabetes.

The Link Between Obesity & Heart Diseases

Heart diseases refer to a group of cardiovascular diseases that includes:

  • Heart attack – a sudden blockage of coronary blood flow and death of heart muscles
  • Heart failure – a progressive weakening of heart function
  • Coronary artery disease – narrowed coronary arteries with fatty plaque deposits, damaged coronary blood vessels, or reduced blood flow to the heart muscles

Similar to the link between obesity and type 2 diabetes, the metabolic and inflammatory effects in obese individuals can bring about various heart diseases. High nutrient levels in the bloodstream and proinflammatory state exert constant metabolic stress on the heart. This eventually deteriorates heart muscle (myocardial) structure and function, resulting in heart failure. Ectopic fat deposition in the heart muscles and vessels also lead to the accumulation of toxic lipids (cardiac lipotoxicity) which causes damage to heart muscles, which is referred to as obesity-related cardiomyopathy. Fatty plaque buildup in the walls of coronary arteries (atherosclerosis) also causes coronary artery disease and can result in a heart attack.

Interestingly, although obesity increases the risk of the onset of heart disease, overweight and obese individuals have been observed to have better heart disease prognosis and lower mortality rates compared to those falling in the normal and underweight (less than 18.5 kg/m2) BMI ranges. This is known as the obesity paradox. However, no clear evidence of protective mechanisms due to obesity have been established, and this paradox may have partly arise due to the poor measure of adiposity (body fat) using BMI. Other factors, such as body fat distribution, nutritional status, and cardiorespiratory fitness, are more medically sound in differentiating obese individuals and determining the link between obesity and heart disease prognosis.

Obesity can also indirectly influence the incidence of heart diseases by causing type 2 diabetes and high blood pressure (hypertension), which have also been found to be responsible for heart diseases.

Diabetes & heart diseases 

Diabetes increases the risk of all heart diseases as the sustained high levels of glucose in the blood (hyperglycemia) damages coronary blood vessels and nerves.

Additionally, a heart muscle disorder, known as diabetic cardiomyopathy, is caused solely by diabetes, independent of coronary artery disease. In diabetic patients, insulin resistance means an inability to utilize glucose, which forces the heart to increase fatty acid (lipid) oxidation for energy instead. This can lead to cardiac lipotoxicity and subsequent damage to the heart. Other diabetes-related effects, such as endothelial (inner arterial lining) dysfunction and scar tissue formation (fibrosis), can also cause changes to heart structure and function and eventually lead to heart failure.

High blood pressure & heart diseases

In obese and diabetic individuals, narrowing and hardening of blood vessels due to ectopic fat deposition and glucose-induced vascular damage increases blood pressure and often leads to hypertension. High blood pressure then induces the hardening of coronary arteries and left ventricular hypertrophy, which is the enlargement and thickening of the wall of the left ventricle which pumps oxygenated blood around your body. Blood flow around the heart is thence hindered or obstructed and can culminate in various heart diseases.

Preventing Obesity, Diabetes, & Heart Disease

Obesity is largely caused by lifestyle factors including diet, sleep, stress, and physical activity. By being watchful and managing these lifestyle factors well, it is unlikely that you will become obese. Here are some good habits to incorporate into your life to prevent obesity and obesity-related diseases:

1. Have a balanced calorie intake by controlling the portion sizes of your meals. You can use a calorie calculator to find out what your recommended calorie requirements are depending on your age, gender, physique, and usual level of exercise.

2. Reduce your intake of fats and sugars by avoiding processed meat, red meat, refined grains, fried food, sweets, and desserts in your diet. 

3. Eat more vegetables, fruits, legumes, fish, poultry, and whole grains as they are more nutrient-dense, low in unhealthy fats and simple sugars, and provide essential vitamins and minerals.

4. Choose healthier oils, such as olive, nut, avocado, and canola oil, and low-sugar and low-fat food products. Avoid food products with high levels of unhealthy saturated and trans fat.

5. Engage in moderate exercise regularly for at least 60 minutes per day for children and 150 minutes per week for adults.

6. Have a regular sleep schedule with seven to eight hours of sleep every night.

7. Try to keep stress levels low by taking breaks and practicing mindfulness.

8. Abstain from smoking and high alcohol intake.

Living with Obesity, Diabetes & Heart Disease

If you or your dependent has been diagnosed with obesity or obesity-related diseases, you can still take steps to greatly improve disease prognosis, prevent further complications, or even reverse existing conditions. Depending on your diagnosis, weight loss programmes or medications may be recommended by your doctor and you should adhere strictly to them to achieve the best results. As medication may be required for long periods of time, you can opt for medicine delivery services for chronic conditions such as diabetes, high cholesterol, and high blood pressure.

Apart from medical intervention, you should also make changes to your lifestyle. Your diet is a key way to do so. Here at Homage, we have prepared a series of dietary guidelines for preventing and managing  prediabetes, diabetes, high cholesterol, and high blood pressure

If you have hypertension or are at risk due to obesity, you can also explore ways to reduce blood pressure.

Homage provides specialised home care services for diabetes care and hypertension care, making it easier for you or your dependent to receive consistent professional aid to improve obesity and obesity-related conditions.

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References
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About the Writer
Samantha Poh
Samantha is an avid environmentalist pursuing her Ph.D. in biology. She promotes better management of nature, agriculture, and diets to empower both human and environmental health. To escape the fracas of deadlines and global issues, she explores the wondrous natural environments around the world and returns with newfound inspiration.
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