Fast Facts

Intermittent Fasting increased Testosterone by 180% in a 1989 study. But more recent studies show that Intermittent Fasting lowers testosterone production. A 2016 study found Intermittent Fasting decreased Testosterone by 24%.

Introduction

Intermittent fasting has exploded in popularity in the health and fitness community.

Many experts claim intermittent fasting can naturally boost Testosterone production and fat loss.

But is there any evidence to support these claims?

Let’s find out.

What is Intermittent Fasting?

Intermittent fasting involves:

• Time restricted feeding. Limiting food intake to certain hours.
• Alternating between fasting for extended periods and eating.

There are several different types of I.F. diets:

• 16/8 Diet: Fasting for 16 hours. Eating all calories in an 8 hour feeding period.
• 5/2 Diet: 2 days of caloric restriction, where you eat 500 to 600 calories per day. For the remaining 5 days, you will eat a normal diet, consuming maintenance calories.
• 24-Hour Fast: Not eating for 24 hours. Only water, tea, and zero calorie drinks. Also known as Alternate Day Fasting.

Studies show that intermittent fasting can: help with weight loss, reduce the risk of cancer, help manage type 2 diabetes and improve cognitive function.

Intermittent Fasting And Testosterone

Is there a link between Intermittent Fasting and Testosterone?

Does Intermittent Fasting Increase Testosterone?

A 1989 study found Intermittent Fasting increased Testosterone by 180% in a 56 hour fast.

Does Intermittent Fasting Decrease Testosterone Levels?

Recent evidence suggests Intermittent Fasting decreases testosterone production. A 2016 study found Intermittent Fasting decreased Testosterone by 24% in young men.

1989 Study

The 1989 study looked at the effects of fasting for 56 hours on Testosterone production.

In 8 lean men, intermittent fasting:

• Increased Testosterone levels by 180%
• Raised Luteinizing Hormone (LH) by 67%

In 9 obese men, intermittent fasting had no effect on Testosterone production or LH.

The scientists concluded:

Fasting impacts Testosterone production differently in lean and obese men. Fasting boosts Testosterone in lean men. Fasting has no impact on Testosterone levels in overweight men.

Röjdmark, 1989

But the study results are misleading:

• All 17 men received an injection of Gonadotropin Releasing Hormone (GnRH).
• GnRH stimulates your brain’s pituitary gland to secrete Luteinizing Hormone (LH). LH stimulates the testicles to produce Testosterone.
• This artificially increased Testosterone production in the 8 healthy men.

Fasting and food restriction reduces Gonadotropin Releasing Hormone (Kumar and Kaur, 2013). This decreases LH and Testosterone levels, as can be seen in more recent studies.

2016 Study

A 2016 study found Intermittent Fasting decreased Testosterone levels by 24%.

The 8 week study looked at the effects of intermittent fasting on Testosterone and body composition in men working out.

The 34 men were split into 2 groups:

• Control group eating a conventional diet
• Intermittent fasting group following time restricted feeding.

All men had the same calorie intake. They all followed the same resistance training programme and worked out 5 days per week.

The study found intermittent fasting for 8 weeks:

• Decreased Anabolic Hormones: Fasting reduced Testosterone levels by 24% and IGF1 by 12.5%
• Increased Growth Hormone: This prevented loss of strength and muscle mass despite Testosterone decrease. Both groups experienced the same boost in muscular strength and athletic performance.
• Lost 13.6% More Body Fat: the intermittent fasting group lost 13.6% more body fat than the control group.
• Increased Insulin Sensitivity: Intermittent fasting reduced blood glucose levels by 11% and improved insulin sensitivity. This reduces risk of Type 2 diabetes.
• Decreased Systematic Inflammation: Fasting had anti inflammatory effects
• No Effect On Cholesterol But Reduced Triglycerides: High triglyceride levels contribute to hardening of the arteries. Lowering triglycerides improves heart health. This shows IF reduces risk of heart problems.

The 2016 study is more accurate than the 1989 study. It had a larger sample size and looked at the long term effects of fasting for 8 weeks.

Intermittent fasting is a good strategy for weight loss, despite lowering Testosterone levels.

How Does Intermittent Fasting Affect Other Hormones?

Fasting has a positive effect on other hormones.

Insulin

Intermittent fasting has a major impact on insulin levels and insulin resistance.

Insulin is a hormone produced by the pancreas. It regulates blood sugar levels and enables your body’s cells to use sugar for energy.

Fasting lowers insulin resistance and reduce the likelihood of developing type 2 diabetes. Another study found that diabetic patients who fasted required less insulin treatment.

Human Growth Hormone

Human growth hormone (HGH) reduces body fat levels. It increases protein synthesis, boosting muscle growth and exercise performance. It also handles cell growth and repair.

Can fasting increase growth hormone?

Intermittent fasting increases HGH levels. In one study, fasting for 24 hours increased HGH by 500%.

Leptin

Intermittent fasting affects leptin.

Leptin regulates appetite. It is the “satiety” hormone and tells your brain when you are “full”.

It tells your brain to:

• Reduce food intake.
• Increase energy expenditure – to start doing physical activity to burn calories.

Obese individuals suffer from leptin resistance. Despite having high leptin levels, they are less sensitive to leptin. As a result, their brain does not receive the signal to decrease appetite and stop eating.

This means they eat more calories than they need, resulting in weight gain and obesity.

Research suggests intermittent fasting increases leptin sensitivity. This leads to decreased appetite and fat loss long term.

Ghrelin

Ghrelin is the “hunger hormone”. It signals your body to feel hungry. Intermittent fasting reduce ghrelin levels, leading to a decrease in food cravings.

Adiponectin

Adiponectin is a hormone produced by adipose tissue (fat cells).

Adiponectin increases fat burning by boosting fatty acid oxidation. It has anti inflammatory effects and raises insulin sensitivity.

Time restricted eating increases adiponectin, leading to increased fat loss and improved health.

Conclusion

There is a clear link between Intermittent Fasting and Testosterone.

Fasting does not boost Testosterone levels. In fact, recent studies show fasting reduces T levels by as much as 24%.

But fasting does leads to better health outcomes:

• It improves body composition, decreasing excess body fat while preserving lean muscle mass. This is especially true when combined with weight training.
• It reduces food cravings and appetite – helping you lose body fat
• It lowers blood glucose levels, improving insulin sensitivity. This reduces risk of Type 2 diabetes.