Chapter 1: Understanding Overweight and Obesity

It is more important than ever to understand the complexities of overweight and obesity, especially in the USA, where over 40% of adults are classified as obese, according to recent CDC data.

While both involve excess weight, obesity represents a more severe condition with a greater likelihood of serious health complications like type 2 diabetes, heart disease and nonalcoholic fatty liver disease.

However, its causes are multifaceted, ranging from dietary imbalances and sedentary lifestyles to genetic predispositions, medical conditions, and even certain medications.

In this guide, we will cover all the aspects related to being overweight and obesity so that you can start your weight loss journey the right way.

What is the difference between Overweight and Obesity?

Overweight refers to a body weight greater than what’s considered healthy for a given height, while obesity is a condition characterized by excessive fat accumulation that poses a significant health risk.

Both indicate excess body fat, but obesity signifies a more severe level, with a greater risk of health complications.

Let’s understand the difference in depth with this table:

What percentage of the US population is overweight and obese?

According to the latest data from the CDC, from August 2021 to August 2023, over 40.3% of U.S. adults were obese.

According to the 2017–2018 NHANES report, 30.3% of Americans were overweight, while 42.8% were obese. Among these, 9.6% were severely obese, which means they had a BMI at or above 40.0.

Source: Centers for Disease Control and Prevention, National Center for Health Statistics

These numbers are staggering and highlight the public health crisis we’re facing. This isn’t just about individual choices; it’s a societal challenge that requires comprehensive solutions.

Are overweight and obese the same thing?

No. While they both involve excess weight, the degree of excess and the associated health risks differ significantly. Overweight is a precursor to obesity and early intervention can prevent progression.

How to calculate obesity and overweight?

We use the Body Mass Index, or BMI, as our primary tool to calculate obesity in adults. But other methods, like waist circumference and body fat percentage measurements, provide more detailed insights.

The BMI Formula

BMI = (weight in pounds / (height in inches x height in inches)) x 703

Let’s walk through an example:

Imagine someone who weighs 200 pounds and is 5 feet 10 inches tall (which is 70 inches).

1. Square the height: 70 inches x 70 inches = 4900 square inches
2. Divide the weight by the squared height: 200 pounds / 4900 square inches = 0.0408
3. Multiply by 703: 0.0408 x 703 = approximately 28.7

So, this person’s BMI would be around 28.7.

What BMI is considered overweight and obese?

A BMI of 25 to 29.9 is overweight, while a BMI of 30 or higher is obese.

There are 3 classes of obesity:

• Class 1: 30 to 34.9
• Class 2: 35 to 39.9
• Class 3 (Severe Obesity): 40 or higher.

How to Calculate Overweight and Obesity in Children

WHO recommends a different methodology to measure obesity and overweight in children between the ages of 0 and 19. This is because age has to be considered as a factor when measuring obesity in children.

For very young children (under 5 years old):

• Overweight – If their weight is much higher than the average for their height (specifically, more than 2 standard deviations above the average), they are considered overweight.
• Obese – If it’s even higher (more than 3 standard deviations above the average), they are considered obese.

For older children and teenagers (5 to 19 years old):

• Overweight – If their BMI is higher than the average for their age (more than 1 standard deviation above the average), they are considered overweight.
• Obese– If their BMI is significantly higher than the average for their age (more than 2 standard deviations above the average), they are considered obese.

What are the causes of obesity and being overweight?

First off, let’s dispel the myth that it’s just about laziness or lack of willpower. That’s a harmful oversimplification. Human biology is incredibly complex.

1. Dietary Imbalances

This isn’t just about eating too much. It’s about the type of calories we consume. For example, highly processed foods which are loaded with refined sugars, unhealthy fats and artificial additives can wreak havoc on our metabolic systems.

They provide a massive dose of calories with minimal nutritional value and our bodies don’t register them the same way as solid food.

2. Sedentary Lifestyle

Sedentary behavior significantly increases with age, with young adults spending roughly 50-60% of their day inactive. Our bodies are designed for movement and when we don’t move, the energy we consume gets stored as fat.

3. Genetics

Genetics plays a significant role. Some individuals are genetically predisposed to store fat more easily or have a slower metabolism.

This study of twins, both those raised together and separately, demonstrated a strong genetic influence on BMI, with heritability estimates ranging from 66-74%, indicating that genes play a substantial role. Conversely, the shared childhood environment showed negligible impact on BMI similarity in later life.

However, genetics don’t determine destiny. They create a predisposition, which can be influenced by lifestyle choices.

4. Medical Conditions

Several medical conditions, such as hypothyroidism, Cushing’s disease, and even depression, can disrupt hormone balance or metabolic processes, leading to weight gain.

Additionally, sleep disorders like insomnia and life stages like menopause can indirectly contribute to weight increase through hormonal changes and lifestyle shifts.

5. Prescription Medications

Many prescription medications, particularly those for diabetes, psychiatric conditions, and hypertension, can lead to significant weight gain by affecting appetite, metabolism, and hormone levels. This side effect is often accompanied by increased risks of metabolic disorders like type 2 diabetes and cardiovascular problems.

What are the health risks of being overweight and obesity?

1. Type 2 diabetes

The accumulation of excessive body fat disrupts normal metabolic processes. This leads to insulin resistance and impaired β-cell function, which are key factors in the development of type 2 diabetes.

2. Nonalcoholic fatty liver disease

The high amount of body fat leads to increased fatty acid delivery to the liver. This disrupts the balance of fat uptake and export, which results in the accumulation of triglycerides and the development of nonalcoholic fatty liver disease (NAFLD). This accumulation is further worsened by insulin resistance and inflammation, both of which are linked to obesity.

3. High blood pressure

When you put on excess weight, especially visceral fat, it compresses the kidneys. This activates the renin-angiotensin-aldosterone system and increases sympathetic nervous system activity, which leads to elevated blood pressure. Over time, this contributes to chronic kidney disease, which makes hypertension more difficult to manage.

4. Sleep Apnea

Fat deposits in the upper respiratory tract narrow the airway. This leads to breathing difficulties and recurrent pauses in breathing during sleep, which characterize obstructive sleep apnea (OSA). This results in decreased oxygen levels, causing sleep disturbances and associated health risks.

5. Osteoarthritis

Arthritis Foundation says, “Being just 10 pounds overweight puts an extra 15 to 50 pounds of pressure on your knees.” This leads to increased stress and accelerated cartilage breakdown. Obesity also contributes to systemic inflammation and hormonal imbalances, further exacerbating joint damage in osteoarthritis.

How to manage overweight and obesity?

One way is the dietary management of obesity, which primarily involves calorie restriction, with low-calorie (800-1500 kcal/day) or very low-calorie (<800 kcal/day) diets.

A typical macronutrient distribution should be 55% carbohydrates, 10% proteins and 30% fats (with limited saturated fats). You can add regular exercise to your diet for faster and efficient results.

While the equation of “calories in versus calories out” seems simple, modern food environments and sedentary lifestyles can make it challenging. This is why medical weight management is often required to deal with obesity.