As you age, you become more likely to gain weight for two main reasons – your physical activity decreases and your metabolism slows down.
One of the factors affecting your metabolic rate may be the changes in your hormonal environment, such as the age-related decline of testosterone (T) in men.
Furthermore, medical conditions that affect T levels can lead to dramatic metabolic changes and rapid weight gain.
On the other hand, obesity can be the underprint for many instances of hormonal imbalance. According to research, its incidence keeps increasing and it has reached a whopping 43% of all US adults in the last few years.
Obesity can lead to low T and an increased risk of erectile dysfunction in men. In women, obesity causes high T levels and the development of male characteristics (virilization).
Therefore, there is a complex interplay between your body weight, testosterone levels, and hormonal balance.
In this article, we will break down these interactions, including the effects of testosterone therapy on your metabolism, obesity, fat loss, and muscle mass.
How does low testosterone cause weight gain in men
Low T in men is associated with a specific type of obesity called visceral. The term describes the accumulation of intra-abdominal fat which builds up around the internal organs and plays a role in insulin resistance, inflammation and atherosclerosis.
Therefore, low T in men may increase the risk of obesity and related conditions such as type 2 diabetes and cardiovascular disease.
Increase in body mass index (BMI) with one unit resulted in a 2% decline of T levels
Furthermore, studies suggest that low T often leads to loss of muscle mass which is likely the main underprint for the lower metabolic rate in testosterone deficiency.
This can make it more difficult for you to lose fat, even if you follow a weight loss diet and exercise regime. Less muscle mass also results in lower energy expenditure during physical activity and sports.
On the other hand, obesity can be a major cause of reduced T production in otherwise healthy men. The effects of having extra fat are more significant than the age-related decline of T in men.
The scientists estimated that an increase in body mass index (BMI) with one unit resulted in a 2% decline of T levels, which is comparable to that associated with approximately 10 years of aging.
One of the underlying mechanisms is that obesity increases the activity of the aromatase enzyme which is found in your adipose tissues. It leads to increased testosterone aromatization and converts more testosterone into estrogens (E).
As your body produces more estrogens, the hormone suppresses the function of the hypothalamic-pituitary-testicular (HPT) axis.
Without HPT stimulus, the testes can’t produce sufficient amounts of T, which may lead to testosterone deficiency (hypogonadism).
Therefore, some researchers define the condition as male obesity-related secondary hypogonadism.
Reduced testosterone production may also occur due to the increased levels of insulin and leptin in obese men. They can suppress the release of gonadotropin-releasing hormone (GnRH) and the HPT axis which leads to low T.
Total testosterone levels are usually more severely affected than free T levels in men since obesity and high insulin levels lower a protein called sex hormone-binding globulin (SHBG).
The connection between testosterone and weight in women
Women with obesity and hyperinsulinemia also experience a decrease in SHBG. This leads to elevated free T levels and the development of conditions such as polycystic ovary syndrome (PCOS).
High T is one of the hallmark signs of PCOS in women. It may lead to the occurrence of acne, deeper voice, increased body, and facial hair growth, and other masculine physical characteristics.
On the other hand, high T is unlikely to cause obesity or insulin resistance in women. Studies are conclusive that elevated testosterone is the result rather than the cause of high insulin and weight gain.
Nevertheless, some hormonal changes during menopause can increase the risk of obesity
The related decline of estrogen may lead to changes in the hormones controlling hunger, resulting in increased appetite, higher intake of calories, and weight gain.
Furthermore, menopause often involves the accumulation of intra-abdominal fat and visceral obesity, which leads to the development of a typical “hormonal” or “menopause belly”.
Visceral obesity in women also increases the risk of type 2 diabetes and cardiovascular diseases.
How much testosterone can be increased with weight loss?
Losing body fat in men can help decrease estrogen, insulin, and leptin levels, which results in improved testosterone synthesis.
According to a study in 58 obese men, weight loss led to a significant increase in total testosterone and SHBG. Free T was also increased, albeit to a lesser extent.
More than half (28) of those men had T levels under 300 ng/ml prior to the intervention which is suggestive of hypogonadism. However, 23 out of 28 men experienced an increase in T above 300 ng/ml after they lost significant amounts of fat.
The exact amount of weight loss required to improve T levels will vary from one individual to another
For example, a trial in 43 severely obese men revealed that they had to lose as much as 15% of their body weight to experience a sufficient increase in their T. Furthermore, weight loss improved their semen quality and fertility.
Related post: Low Testosterone and Male Infertility
Another study investigating the effects of different calorie-matched weight loss diets reported similar effects on T levels in 118 obese men. The increase in T depended on the amount of weight loss rather than the diet as long as it creates an energy deficit.
Increasing your physical activity is another effective method for creating a deficit and losing weight. Yet, some types of exercise may provide additional benefits for your T production compared to others.
According to one study, 4 weeks of training with weights led to a 36% increase in average T levels in men afterward. In contrast, evidence suggests that women may experience only short-term increases in T levels during resistance training.
Another form of exercise – high-intensity interval training (HIIT) appears to increase testosterone in men but lowers in women. On the other hand, cardio does not affect or may even lower testosterone in both men and women.
Bariatric surgery is also a highly effective method for weight loss. It works by surgically restricting the volume of the stomach and thus helping the patient achieve fullness after a meal much faster.
In one trial, sleeve gastrectomy and gastric bypass surgery in 40 men led to significant weight loss and an increase in their T levels. Patients also improved their cardiovascular condition, measured by the reduced thickness of their arteries.
Does taking testosterone cause weight gain or loss?
If you have low T levels which cause any symptoms, then you may be eligible for testosterone replacement therapy (TRT). Since low T often leads to weight gain and increases the risk of obesity, taking TRT can reverse the process.
The treatment will normalize your T levels and boost fat loss, while at the same time you will retain or even increase your muscle mass.
The onset of effects of testosterone treatment usually begins as soon as the 3rd week of therapy.
Yet, the improvements in body composition and fat mass are most noticeable after the 3rd month of TRT. Furthermore, a review of multiple studies reveals that it takes several months or years of therapy until you will achieve the maximum benefits.
The magnitude of the effect depends on the dosage of the therapy. Scientists report that higher dosage increases the benefits of T on body composition.
In general, TRT should be dosed individually with the aim to avoid side effects and achieve serum testosterone levels in the mid to high normal range.
Testosterone exhibits its fat-burning effects by increasing the levels of lipolytic beta-adrenergic receptors and reducing the activity of lipoprotein lipase (LPL) in adipose cells.
The beta-adrenergic receptors mediate the release of fat from adipocytes under the effect of adrenaline. As a result, the fat cells shrink, while blocking the LPL enzyme prevents the fat from returning back inside.
Furthermore, testosterone therapy may have moderate benefits for insulin sensitivity and glucose control which are likely a result of its effect on fat loss.
What is the best form of TRT for fat burning?
TRT is available in different forms, including intramuscular injections, transdermal gels and patches, subcutaneous implants, and oral tablets.
The effect of the therapy depends on the achieved serum T levels and the dose, rather than the form of TRT. All forms of TRT are effective in reducing fat in patients with hypogonadism.
Testosterone injections have the best bioavailability and lead to the quickest rise in blood T levels. For example, injectable testosterone enanthate leads to an increase in serum T levels immediately after administration.
Therefore, T injections will likely result in the quickest weight loss compared to other TRT forms.
Alternative methods for increasing T such as testosterone boosters and supplements do not appear effective in increasing fat burning. In fact, scientists warn that the majority of T boosters are not effective in increasing testosterone in the first place.
Researchers suggested that about 10% might have testosterone reduction rather than boosting effect in healthy individuals
Only one supplement called dehydroepiandrosterone (DHEA) appears to successfully increase T levels in healthy subjects although they still remain within the physiological limits. The supplement leads to a significant increase in estrogen as well.
Yet, research reports that there are no significant effects of DHEA on body composition and fat loss in young or older adults.
Get a free consultation with our medical expert for any questions about hormone replacement therapy