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Obesity in Adults: the Reasons of Unexplained Weight Gain

Medzone  >  Obesity in Adults: the Reasons of Unexplained Weight Gain

Obesity is more than just weight gain. It is a complex disease that furthers the risks of potentially life-threatening medication conditions. In this comprehensive review, we look at the facts surrounding obesity in adults, the reasons of unexplained weight gain, how hormones influence body fat, how increased weight gain influences hormone levels, and what can be done to reduce fat retention and storage.

The facts about obesity in adults in the US are staggering:

  • In 2017 – 2018, 42.4% of the US population was obese
  • Some of the leading causes of premature, preventable deaths in the US are type 2 diabetes, stroke, heart disease, and certain types of cancer
  • Annual medical costs associated with obesity are $1,429 higher per person than those with normal weight

Some people can pinpoint the cause of rapid weight gain – overeating. A sudden weight gain such as this differs from unexplained causes where there is no reason for the change.

That is what we look at today – why weight increases unexpectedly and what to do about it. However, before we can address the problem, we need to know what obesity is.

Obesity is having a weight that is greater than what is considered healthy for a person’s height and bone structure. We turn to BMI (body mass index) to define obesity and explore this further in the next section.

Obesity in adults is a significant problem in the US – one that requires addressing.

Facts About Obesity and Overweight

As we begin our exploration into obesity in adults, we focus first on the definition, diagnosis, classes, symptoms, and treatment of obesity in general. In future sections of this report, we look more closely at underlying and contributing causes and how to address those situations.

Obesity classification is a system used by The World Health Organization (WHO) that helps define disease risk associated with being overweight.

Definition of Obesity

Obesity is a chronic medical disease associated with having high amounts of body fat.

Diagnosis of Obesity

BMI is the primary tool used to calculate obesity and can be assessed at home by entering your height and weight in an online tool. However, BMI does not tell the entire story, as many bodybuilders may have a high BMI but very little body fat. Excess muscle mass increases weight, so that can show a BMI that would seem to fall into one of the classes of obesity below.

Other tools used to measure, and monitor body fat require medical assessment, and some can be costly:

  • BOD POD: a person enters a computerized, egg-shaped chamber that measures body mass and volume to determine body fat and lean muscle
  • Hydrostatic Weighing: an underwater calculation of lean body mass to body fat utilizing costly equipment
  • Dual-Energy X-ray Absorptiometry (DEXA): X-rays that measure bone density as well as body fat percentage and the location of the body fat
  • Skin Calipers: a metal tool that measures the thickness of a layer of fat in a skinfold
  • Bioelectric Impedance Analysis (BIA): Two different methods measure BIA:
    • Placement of electrodes on a wrist and ankle, as well as the top of the foot and back of the right hand to measure the voltage between the electrodes to determine body fat
    • Standing on footpads on a special scale while an electrical current moves through the body to calculate body fat percentage


Classes of Obesity:

Obesity classification plays a vital role in assessing health risks. Individuals with a BMI of under 18.5 are considered underweight. A BMI of 18.5 – 24.9 falls into the healthy or normal weight sector. Most individuals (bodybuilders and muscular athletes excluded) in the 25.0 to 29.9 range are considered overweight and pre-obese.

  • Class 1 obesity: individuals who fall into obese class 1 (30.0 – 34.9 BMI) have a high to very high risk of developing diseases such as hypertension (high blood pressure), cardiovascular disease, and type 2 diabetes
  • Class 2 obesity: individuals with obese class 2 (35.0 – 39.9 BMI) have a very high risk factor for these health issues
  • Class 3 obesity: adults in obese class 3 (40.0 + BMI) are at an extremely high risk

Waist circumference is another predictor of health risk, as shown in the chart below (for men):

Waist Circumference in Men Low Risk High Risk Very High Risk
Less than 94 cm X
94 to 102 cm X
Greater than 102 cm X

And for women:

Waist Circumference in Women Low Risk High Risk Very High Risk
Less than 80 cm X
80 to 88 cm X
Greater than 88 cm X

Adults who fall into the class 1 obesity category have an increased health risk with low waist circumference, moving from high to very high as their circumference expands.For individuals who fall under the overweight category, having a low waist circumference poses no increased health risk. A high waist circumference increases the risk of health concerns, while a very high one confers a high health risk.

Symptoms of Obesity

Many people do not realize that other health issues they have are also symptoms of obesity, such as:

  • Sleep apnea
  • Breathlessness
  • Low self-esteem
  • Increased sweating
  • Difficulty walking
  • Gallstones
  • Osteoarthritis
  • Body aches
  • Fatigue
  • Fatty liver
  • High cholesterol
  • Gout
  • Some types of cancer
  • Heart disease
  • Hormonal imbalance
  • Infertility

Treatment for Obesity

There is no simple cure for obesity. Treatments can range from diets to exercise to surgery. Some people may benefit from weight loss medications. If weight gain is due to emotional eating, a person may benefit from counseling. Ultimately, the best treatment will be based on numerous factors, looking at the cause (or causes) of the weight gain, and addressing those concerns.

For individuals wondering how to lose weight fast, be careful of fad diets. These can lead to dramatic and rapid weight loss followed by weight gain after the program ends. Working with a doctor who specializes in safe and healthy weight loss is beneficial for some people.

Most Common Causes of Overweight

Most Common Causes of Overweight

For many people, the cause of obesity in adults is overeating. Quite simply, that means consuming more calories each day than you expend. Men and women who have active lifestyles can safely consume more calories than those who have sedentary lifestyles. If you want to lose weight, you must expend more energy than you consume in calories.

However, there are other causes of weight gain and obesity to address – many that have nothing at all to do with overeating. After all, there are plenty of people who consume very little food and still wind up gaining weight. For them, it may be that their bodies are working against them in some way. That is what we address below in answer to the question “what causes obesity” in adults.

Food Quality and Addiction

  • A diet high in processed and fast foods does not provide the body with the same nutrients as fresh fruits, vegetables, and lean protein. High-calorie beverages, fried foods, packaged foods, chemicals, and oversized portions lead to weight gain.
  • Food addictions are caused by many factors, including the chemical engineering of products that cause you to get hooked on them. Remember the advertisement that said, “you can’t eat just one?” Comfort foods make us feel good, especially in trying times. High-fat junk food, sugar-sweetened items, and heavily processed foods work on the reward centers in the brain the same way nicotine, alcohol, caffeine, and other drugs do.
  • Food availability is a problem for many people. High-quality food may not be readily available in some areas, or it may cost more than lower-quality, unhealthy items. Consuming a lot of simple carbohydrates rather than complex ones can increase fat retention.

Inactivity and Lifestyle

  • Hours spent at a desk, in front of a computer or TV screen, or not engaging in physical activity, reduces the calories expended.
  • High intakes of alcohol, sweetened oversized coffee drinks, and other detrimental lifestyle habits can increase weight gain.
  • Lack of sleep can disrupt critical hormones that regulate metabolism and lead to weight gain.

Hormonal Imbalance

Hormones play a significant role in metabolism and deserve their own section below.

Stress Level

Stress influences obesity in adults in many ways. The hormonal connection is via increased levels of cortisol, which we address below. Stress often leads to overeating for comfort, as well as isolation and lack of exercise.

Medical Conditions

The following are some of the many medical conditions that can increase the risk of weight gain and obesity in adults:

  • Arthritis
  • Cushing syndrome
  • Hypothalamic damage
  • Hypothyroidism
  • Insulin resistance
  • Prader-Willi syndrome
  • Polycystic ovarian syndrome

Certain medications in the following categories can also lead to excessive weight gain:

  • Antidepressants
  • Antihistamines
  • Antipsychotics
  • Anti-seizure drugs
  • Beta-blockers
  • Blood pressure drugs
  • Corticosteroids
  • Diabetes medications
  • Oral contraceptives
  • Pizotifen
  • Steroids


Specific gene variants can play a role in weight gain, and they can also affect hormones and fat regulation. Family genetic patterns can increase obesity risk, especially when environmental and lifestyle factors are figured in. Since families tend to share many of the same unhealthy habits, children with obese parents are more likely to become obese themselves. Genetic predisposition may also make it harder to lose weight through traditional methods of diet and exercise.

Ethnicity is another factor, with African-American and Hispanic women more likely to gain weight at an earlier time than Asian and Caucasian women. The same applies to men in those groups, although the difference is not as high.

As we look further at what causes weight gain, factors such as pregnancy and quitting smoking are two other issues. Many women have trouble losing some of their pregnancy weight gain after giving birth, which can lead to obesity. Although quitting smoking has many health benefits, some people turn to food during this time. It is crucial to find other methods of controlling those cravings to avoid weight gain. Using a cinnamon stick in place of a cigarette (do not light it) helps with cravings and may combat some of the psychological withdrawal symptoms.

Facts About Obesity and Overweight-min-min

Hormonal Weight Gain: How Hormones Can Affect Our Weight

Changes in hormone levels can also cause obesity in adults.

How can hormone imbalance cause weight gain?

The body’s many hormones are our chemical messengers. They relay critical signals that regulate every function in the body. If any hormone is out of balance, it can have a snowballing effect on many others. Many hormones regulate appetite, metabolism, fat accumulation and distribution, and glucose usage.

Obesity in adults is often associated with changes in the following hormones:


One function of insulin is to help regulate carbohydrates and fat metabolism. Insulin makes the body’s cells sensitive to the signals of glucose, so the cells take in the glucose to use for energy. When insulin resistance occurs, glucose levels remain high in the bloodstream, causing the liver to take in and store more blood sugar (fatty liver disease risk). Excess glucose enters the fat cells, increasing weight gain.

Human Growth Hormone

Growth hormone is one of the primary metabolism-regulating hormones. It also helps regulate muscle mass and body composition. Adults who have low GH levels are more likely to have a higher fat to muscle ratio. GH promotes the production of insulin growth factor 1 in the liver. Growth hormone and IGF-1 work to influence protein, lipid, and carbohydrate metabolism, improve energy expenditure, and inhibit fat accumulation. Lower GH levels in older adults increase the risk of obesity and the progression of metabolic diseases.


Thyroid dysfunction is often implicated in weight gain, food intake, body composition changes, and lipid and glucose metabolism. Hypothyroidism is associated with weight gain and reduced metabolic rate.


Stress and lack of sleep are two issues that can result in elevated cortisol production. Cortisol keeps the mind and body in a state of high alert, making it harder to fall asleep at night. That reduces the amount of time the body has for secreting growth hormone and testosterone into the bloodstream. The metabolism slows down and cannot properly process food. Cortisol also causes the protein stores in muscle to breakdown into glucose for fuel. That is why people on low-calorie diets tend to lose muscle rather than fat.

With extra glucose entering the bloodstream, the cells often cannot take it all in, and it turns to belly fat. Additionally, stress interferes with the thyroid gland, affecting thyroid hormone production. Finally, because fatigue sets in when you do not get enough sleep, cortisol stimulates the hunger hormone ghrelin, which often leads to overeating when the body needs energy.


Fat cells (everyone has them) produce leptin, which enters the bloodstream and works on specific areas of the brain to help control appetite. However, in people who are overweight, leptin resistance often occurs. Instead of reducing appetite, leptin levels just build up in the bloodstream and do not let the body know when it is full, often resulting in overeating. Leptin levels also decline during low-calorie dieting, fasting, and uncontrolled type 1 diabetes.

The result in these situations is an increase in hunger, and the body decreases energy expenditure by holding on to stored fat. Leptin also plays a critical role in glucose and lipid metabolism, insulin sensitivity, lipogenesis, lipolysis, and other essential functions relating to fat metabolism.

Sex Hormones

Estrogen and testosterone play a critical role in fat storage and usage. Testosterone helps regulate how the body metabolizes the food it consumes, converting it into usable energy. However, the body also converts some of the free testosterone into estrogen. An enzyme in belly fat (aromatase) converts the testosterone. Estrogen goes on to promote fat storage, which then increases aromatase and further lowers testosterone and metabolism capabilities.

Male obesity is often associated with low total testosterone and sex hormone-binding globulin (SHBG) levels. SHBG is the protein that transports testosterone through the bloodstream to the androgen receptors. Low SHBG leaves more testosterone free in the bloodstream available for aromatase conversion to estradiol (estrogen). Long-term obesity also reduces the number of Leydig cells that produce testosterone, causing a further reduction in testosterone levels.

In women, central obesity is often associated with higher testosterone levels, as seen in females diagnosed with polycystic ovarian syndrome (PCOS). For women, both low and high testosterone levels can lead to weight gain. Estrogen deficiency is also a problem as it further promotes metabolic dysfunction and can lead to obesity and type 2 diabetes. It is even more crucial for them to protect testosterone/estrogen balance.

Obesity in adults is often linked to changes in hormone levels – especially when no other underlying causes are present.

Hormonal Belly Fat or Abdominal Fat

Visceral abdominal fat is the most dangerous type of fat to have as it attaches to internal organs such as the pancreas and liver. Hormonal belly fat associated with changes in hormone levels can lead to an accumulation of intraperitoneal fat that can pose a significant health risk, more so than gynecoid or gluteofemoral obesity.

As we look at obesity in adults, it is the visceral belly fat and not the subcutaneous fat (the fat you can pinch between your fingers) that can increase the risk of metabolic syndrome.

What causes belly fat?

Let’s look at the answers below and how to treat the situation:

What Causes Abdominal Fat (also called intra-abdominal fat)

When it comes to hormones, both growth hormone deficiency and hypogonadism (low testosterone) are associated with abdominal weight gain. As changing hormone levels encourage fat accumulation, the metabolism resets itself in a way that lends itself to further weight gain. Metabolic syndrome, PCOS, menopause, andropause, and even IVF fertility treatments can all increase abdominal fat storage.

Most Effective Ways to Lose Belly Fat

The most effective ways of treating belly fat are those that deal with the causes. If a hormonal imbalance is present, restoring proper balance will often improve metabolic functions. When there is an underlying health condition, the appropriate treatment can do wonders for reducing stored body fat.

Even a modest 5 to 10 percent loss of weight can help reduce the risks of heart disease and diabetes.

Hormonal Belly Fat or Abdominal Fat

Weight loss relies on many factors working together for the attainment of a common goal – in the case, that goal is ridding the body of excess fat and improving overall health. Following a healthy diet, cutting back on alcohol, drinking plenty of water (many experts recommend half the body weight in ounces each day), and getting plenty of exercise are important. Reducing stress and getting adequate sleep (7 to 9 hours per night) are also crucial.

Slowing down when you eat – mindful eating – can also help you lose unwanted belly fat. The faster you eat, the more calories you are likely to consume before you feel full. Using a smaller plate will also help you eat less at each meal. Know your triggers and food trips – avoiding them can help equal success. Allow yourself the occasional small splurge or treat. Deprivation leads to failure – a few bites of ice cream or cake, eaten slowly, can satisfy that sweet tooth.

Abdominal obesity in adults causes problems for the internal organs.

Effects: What Obesity and Overweight Can Lead To

The effects of obesity in adults can increase the risk of mortality and morbidity significantly. Before we give a detailed look at some of the primary diseases associated with obesity, we want to answer some frequently asked questions:

Can being overweight cause shortness of breath?

Yes, being overweight puts more of a strain on the heart and lungs.

Can being overweight cause back pain?

Yes, any joint in your body can suffer under the added stress of excess weight.

Does being overweight cause snoring?

Yes, excess fatty tissue and poor muscle tone, especially around the throat or neck, can increase the risk of snoring.

Can being overweight cause sleep apnea?

Yes, obesity or being overweight is one of the leading causes of sleep apnea. Losing weight often remedies the situation.

What Obesity and Overweight Can Lead To - Snoring, back pain, high blood pressure

Does being overweight cause high blood pressure?

Yes, being overweight often causes blood pressure to rise. Losing weight lows the risk and can return blood pressure levels to normal.

Here is a list of some of the primary diseases caused by obesity:

  • Body pain leading to a reduced ability for physical movement and functioning
  • Certain types of cancer (breast, colon, endometrial, gallbladder, kidney, liver, ovarian) – many types of cancer increase in risk when estrogen levels are high, and estrogen tells the body to retain fat, which increases testosterone conversion into estrogen through the enzyme aromatase mentioned before
  • Chronic inflammation, which can increase oxidative stress
  • Chronic obstructive pulmonary disease (COPD)
  • Coronary heart disease and stroke – these risks are compounded by conditions such as high cholesterol and blood pressure levels
  • Digestive diseases – obesity increases the risk of developing fatty liver, heartburn, and gallbladder disease
  • High LDL and total cholesterol and triglycerides, low HDL cholesterol
  • Hypertension (high blood pressure) – a common condition in obesity, especially in women
  • Infertility – both men and women have an increased risk of infertility when they are overweight
  • Insulin resistance – fat cells are more resistant to insulin than muscle cells, so they hold on to the fat they have stored, causing a build-up of insulin in the bloodstream
  • Mental illness (anxiety, depression, other mental disorders) – associated with hormonal changes, self-image, and social isolation factors
  • Metabolic syndrome – risk factors include weight gain, high blood pressure, glucose, and cholesterol levels
  • Osteoarthritis – the increased stress on the bones erodes the joints, and obesity furthers inflammation which can worsen arthritis and pain
  • Reduced quality of life and social isolation
  • Sleep apnea – obesity is a leading factor in serious breathing disorders during sleep which can further increase cardiovascular risks
  • Type 2 diabetes – obesity influences insulin resistance and how the body uses glucose – when insulin and glucose levels build up on the bloodstream, it leads to high blood sugar and diabetes.

When obesity in adults is due to hormonal changes, we can help

How Can We Help?

When obesity in adults is due to hormonal changes, we can help. Many of the health problems people suffer from as they age are a result of declining hormone levels such as testosterone and growth hormone. Balancing those critical hormones can help improve metabolism, fat burning, insulin sensitivity, glucose uptake, and overall health.

Hormone replacement therapy is a medical specialty. You want to find a doctor who specializes in this area of medicine for the best and safest results. We are a national hormone clinic – that is all we do. You will not find our doctors suggesting bariatric surgery, liposuction, or complicated treatments.

What we will do is assess your hormone chemistry through blood analysis to determine if a hormonal imbalance or other medical issue is at the basis of your inability to lose weight. Only then can we put together a program that will help you succeed.

Yes, it is also up to you to make some changes in your life, especially if poor lifestyle choices and habits are causing you to gain weight. Getting proper sleep and exercise are crucial – even if it means taking a ten-minute walk each night and going to bed a few minutes earlier. The smallest changes will start to add up.

Through hormone treatments such as HGH and testosterone, we bring the body back into hormonal balance. As a result, you will begin to experience a change in body composition. Fat storage decreases and lean muscle mass increases. Our clients have had tremendous success in restoring hormonal balance and improving their body composition.

HGH therapy provides many benefits to the body, and the list below highlights the ones that have to do with reducing obesity in adults:

  • Improving lipid profiles
  • Decreasing joint pain associated with osteoarthritis
  • Lowing diabetes, cancer, cardiovascular, and all-cause mortality risks
  • Reducing blood pressure

Along with significant weight loss, HGH therapy results also influence immunity, brain functions, appearance, and emotional well-being, improving a person’s quality of life in multiple ways.

Not only does testosterone therapy also help in many of those same ways, but it also plays a significant role in sexual desire and performance for men and women. Obesity can cause many people to lose interest in sex, whether it is due to actual physiological changes or a lack of self-image. Losing weight and increasing testosterone levels works wonders in the bedroom.

To learn more about obesity in adults, or to speak with a hormone specialist about your situation, please contact our clinic for a free, confidential consultation by phone.

Suspect that you are overweight due to hormonal imbalance? Our hormonal experts will help you find the true reason and give recommendations for further action.
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