What Is Intermittent Fasting?
Simply put, intermittent fasting (IF) is a pattern of eating in which you cycle between periods of eating and fasting. There are three main approaches to intermittent fasting:
- The 5:2 Diet: You consume 500 to 600 calories daily on two non-consecutive days of the week, and eat normally on the other five days
- Eat-Stop-Eat: Involves fasting for 24 hours on one or two days a week; you might not eat from dinner one night until dinner the next night, for example
- Leangains protocol: Also known as the 16/8 method, the Leangains protocol restricts your eating to an 8-hour window out of the 24-hour day; you only eat between 1 pm and 9 pm, for example
What Are the Benefits of Intermittent Fasting?
IF provides health benefits across all body systems:
- Increases your metabolism
- Helps you lose weight and belly fat
- Regulates circadian rhythm to improve sleep quality
- Improves immunity through its effect on the GI tract (where most of your immune system resides)
- Induces several cellular repair processes
- Reduces oxidative stress and inflammation
How Does Intermittent Fasting Affect Your Hormones?
Hormones are your body’s chemical messengers – they help your body and brain communicate about reproduction, stress, sleep cycles, and even hunger and metabolism to turn food into fuel or fat. Intermittent fasting affects many hormones, including insulin, HGH, leptin, ghrelin, thyroid hormone, your sex hormones, and others. Periods of fasting can also affect whether the body uses these hormones well or is resistant to these hormones.
Intermittent fasting and insulin resistance
Intermittent fasting reduces insulin resistance – this is good! Insulin is a hormone that “unlocks” your cells so that they can absorb sugar from your bloodstream to use as fuel. Insulin resistance is a condition where body cells ignore the effects of insulin, which allows blood sugar levels to rise, damage organs, and lead to Type 2 Diabetes.
Intermittent fasting and leptin resistance
Intermittent fasting reduces leptin resistance. – you want this effect as well! Leptin’s job is to help your body maintain its weight by telling the brain when to feel full and that the body should stop eating. Leptin is directly connected to body fat – leptin levels increase as body fat increases. Your brain notices this increases and tells your body that it has had enough food. Leptin levels fall when body fat decreases. Your brain notices the decline in leptin and tells the body that it should feel hungry. In leptin resistance, the brain does not notice high levels of leptin so it thinks the body it should continue eating. Intermittent fasting helps improve leptin resistance, so your brain has a better picture of whether or not the body should stop eating.
Intermittent fasting and ghrelin
Periods of fasting has a positive effect on the hunger hormone, ghrelin. While leptin turns your appetite off, ghrelin turns your appetite on – this hormone causes you to feel hunger. If you want to lose weight and keep it off, you need to tune down your ghrelin levels so you don’t feel hungry.
Intermittent fasting slowly decreases overall ghrelin levels so that, while you may feel hungry at first, you will eventually feel less hungry during fasting periods.
Intermittent Fasting and Your Metabolic Hormones
Intermittent fasting and cortisol
Cortisol prepares your body to deal with stressful situations by diverting resources, such as blood sugar or glucose, to give your body the energy it needs to respond to a stressor or crisis. Cortisol is in a class of hormones called glucocorticoids, which get their name because of their intimate relationship with glucose (sugar) metabolism. This means that cortisol raises blood sugar levels, even during periods of fasting. This can lead to storing more fat – the exact opposite effect than what you’re looking to achieve.
People with adrenal dysfunction or chronic stress should be careful with intermittent fasting. These individuals should start slow and engage in intermittent fasting only under medical supervision, so as not to incur too much stress on the body at once, which can lead to increased fat and worsened adrenal function.
Intermittent fasting and thyroid hormones
The thyroid gland, located at the base of the neck, releases several hormones that regulate metabolism. These hormones include T3 and T4, which together regulate how fast body cells metabolize food. Intermittent fasting can lower T3 and T4 levels, which can actually lead to weight gain, so most patients benefit from thyroid support during intermittent fasting. People with thyroid problems should only participate in intermittent fasting under the care of a doctor.
Effects of Intermittent Fasting on Women vs. Men
Women may be more sensitive than men to the effects of intermittent fasting, largely because women tend to have higher levels of kisspeptin, a hormone that initiates the release of other hormones. Kisspeptin is a key regulator of reproductive hormones (estrogen and progesterone), and is responsible for menstrual cycles and other functions in the body. Intermittent fasting can alter kisspeptin levels and potentially disrupt menstrual cycles. To reduce this effect, women who want to engage in intermittent fasting can start with 12- to 16-hour fasts that start after dinner and continue through breakfast.
Periods of intermittent fasting can increase testosterone by stimulating the production of luteinizing hormone (LH). LH causes a man’s body to produce more testosterone. Most research focuses on the 5:2 method for increasing testosterone in men.
Fasting also increases the brain’s production of Human Growth Hormone (HGH) in both men and women. HGH has multiple benefits over several body systems and is one of the most sought after hormones in Age Management Medicine because of its overarching health benefits.
Intermittent fasting can certainly affect hormone levels both positively or negatively depending on the individual. In order to maintain healthy hormone levels through fasting and optimize the result for weight loss, improved metabolism, and overall health, it is always best to be under the care of an Age Management and Hormone Optimization specialist.
Free Quiz: Are You At Risk For Hormone Decline?
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