What Is Intermittent Fasting?
To recap, we’re basically talking about meal skipping. IF is a dietary protocol where people don't eat for extended periods of time, but can drink water and typically black coffee or plain tea. There are a few popular models:
- 16/8: You fast for 16 hours per day, including your sleeping hours. For most people, this is just skipping breakfast or dinner.
- Eat Stop Eat: You fast for 24 hours once or twice a week.
- Alternate Day Fasting (ADF): Every other day you go without food, with no calorie restriction on your feeding days.
- 5:2: Your “fast days” are really just low calorie days of about 500 calories. It’s debatable as to whether this should actually be considered IF.
There are plenty of people who don't eat for days at a time, but we're focusing on the more popular methods that involve not eating for more than thirty-six hours.
Skipping meals does not slow down your metabolism or make you more likely to store fat, and eating more frequently does not raise your metabolism or help you lose fat.
[Get more in depth in our complete introduction to intermittent fasting!]
There is a debate about whether fasting is better for fat loss or not. Some studies say it is and some studies say it is not. The evidence suggests that there is not much difference in terms of fat loss, but many people find it more satisfying to eat one or two larger meals rather than smaller meals throughout the day. This is a matter of personal preference.
So what about the sex differences?
Why Fasting Can Be Harder for Women
Some of the weight gain could be related to hormones,” says Dr. Aastha Kalra, a New York-based physician who often prescribes fasting to her patients. “In general, there’s something called gonadotropin releasing hormone in everyone. The gonads produce hormones in response to stimulation, so for females, this stimulation causes the ovaries to release progesterone, and in males, it causes the testes to produce testosterone.
The process of ovulation is highly regulated in women, as it is reliant on cycles and schedules. There is a possibility that the hormone that controls ovulation, Gonadotropin releasing hormone, is more easily disrupted by changes in habit and routine for women. So if a woman skips a meal, it can cause more discomfort than it would for a man.
This means that women may feel hungrier when they are fasting, compared to men. More research needs to be done on this topic to determine the exact effect of fasting on metabolism, but it is reasonable to conclude that the hormonal changes caused by fasting can impact metabolism.
This is one possible explanation that Dr. Kalra notes needs more research. However, some studies on rodents have found that fasting negatively affects reproductive hormones in females. Limited research on humans has suggested that women may tend to have greater difficulty suppressing hunger during fasts.
Some studies have found that men become more relaxed while fasting, while women become more stressed.
Insulin Sensitivity
Some people prefer IF for fat loss because it involves abstaining from food, which leads to no insulin being released. In other words, you may be more responsive to insulin because your body isn't producing as much of it. Insulin helps the body absorb nutrients and process carbohydrates, so many people see it as essential for successful weight loss.
There is very limited research on the effects of alternate day fasting on women, but a 2005 study found that it can adversely affect glucose tolerance, which is associated with insulin sensitivity, in women.
However, larger, higher quality studies refute this. A study of 100 overweight or obese women showed that 6 months of intermittent fasting decreased insulin levels by 29% and improved insulin sensitivity.
According to Dr. Kalra, a study found that Doing Intermittent Fasting (IF) for 8-12 weeks can decrease insulin levels by 20-31% and blood glucose levels by 6% in people who have prediabetes. The study also found that there wasn't much difference in insulin sensitivity between men and women.
More research is needed in this area, and while the research is not conclusive, the higher quality studies (especially the randomized controlled trial) show that insulin sensitivity may not be as big of a concern as some people thought.
Fasting and Autophagy
Fasting also has the benefit of promoting autophagy, which refers to the body's natural process of breaking down and recycling old or damaged cells. Fasting has been shown to increase autophagy, especially in the brain, which may explain its link to lower risks of some neurodegenerative diseases.
A 2009 study on mice found that male mice experience significantly more autophagy in their brains when fasting than female mice.
More research is required to determine the differences in autophagy between men and women, according to Dr. Kalra. We understand that autophagy has benefits, but the timing of when it occurs might be different for men and women.
There is not enough evidence to show that there is a difference in autophagy levels between males and females.
Fasting and Cholesterol
Fasting may have different effects on men's and women's heart health, with women possibly having better results.
According to a study published in Obesity in 2010, there was little difference between the effects of alternate day fasting on men and women when twelve women and four men underwent ten weeks of the fasting method.
A study published in Clinical Nutrition ESPEN showed that fasting improves HDL, or ‘good' cholesterol, and that women actually showed greater improvements than men. Similarly, the study showed that women have slightly lower levels of triglycerides than men, so there might be some correlation between women's improved heart health and their lower risk of stroke.
Despite some research findings, more research isstill needed to determine the effect of fasting on cholesterol and triglycerides levels.
Benefits of Intermittent Fasting for Women
Supports Fat-Burning and Weight Loss
When not eating, your body does not have access to the energy from food and must therefore find other ways to sustain itself. After breaking down stored glycogen, your body starts to break down stored fat into molecules called ketones. Ketones replace glycogen as fuel for your cells. As you become more accustomed to a fat-rich diet, your body becomes better at metabolizing fat and burning it for energy. Intermittent fasting has been shown through studies to be effective in aiding fat and weight loss, as well as reducing obesity. [1]
Supports Cellular Renewal and Repair
Studies have found that fasting aids the process of autophagy. During autophagy, your body breaks down old, damaged, and abnormal cells and recycles them for energy. The idea of this text is that by getting rid of old cells, it leaves room for the body to create new, healthy cells. Additionally, it helps with cellular repair and regeneration, inhibits the growth of abnormal cells, and keeping your cells and tissues healthy. [2] [3]
Increases Stem cell Production
Fasting resets your immune system by allowing your body to go into repair mode. The number of stem cells in your body increases because they are the primary repair system in your body. Stem cells are cells that can transform into many different types of cells in order to repair various parts of the body. If you fast, your stem cells will increase in number in your intestines, muscles, and brain. This will help to preserve your stem cells' long-term ability to regenerate independently. [4] The way this works is pretty amazing. During a fast, our bodies reduce our energy expenditure by shrinking tissues, organs, and populations of different cells in our blood. This includes a 28% decrease in white blood cells.
Reduces Inflammation
Many chronic disorders and diseases are caused by chronic inflammation. Fasting can lead to a reduction in the production of inflammatory pathways, as well as a reduction in the activity of chronic inflammation. The positive effects of being physically active can improve your physical and mental health, as well as reducing your risk of developing certain diseases. [5] [6] [7]
Improves Energy
If you want to improve your energy, becoming fat-adapted and experiencing ketosis through fasting is a good option. The improvement is due to an increase in mitophagy, which is a process of breaking down old, damaged, or dysfunctional mitochondria and replacing them with new and healthy mitochondria. Mitochondria are the energy factories in all our cells. If you improve the health of your mitochondria, it can help increase the energy of your cells and make them more efficient. [8]
Supports the Gut
If you give your gut a break from eating, it will have a chance to rest. Digestion takes a lot of energy. When fasting, your body can use the energy that would normally be used for digesting food to repair tissues. Fasting supports the growth of new intestinal cells, which helps to heal a leaky gut and improve overall gut health. [9]
Improves Insulin Sensitivity
Insulin is a hormone that is responsible for regulating the levels of sugar in the bloodstream. Frequently consuming carbohydrates (sugars) increases insulin resistance and inflammation. Insulin is a hormone that helps your body use glucose. If there is too much sugar in your bloodstream, your cells will stop responding to insulin, which will prevent sugar from entering the cells. We call this “insulin resistance” or “pre-diabetes.”
If your cells become resistant to insulin, your body will secrete more insulin in an effort to force the cells to open and take in more sugar. If you keep eating sugar, the insulin-producing cells in your pancreas will eventually stop working. The inability to produce insulin results in toxic levels of glucose in the body, which is diabetes–a debilitating and deadly disease. If you IF, it can increase your body's ability to use glucose in your blood properly. [10] [11]
Lowers the Risk of Chronic Disease
Fasting reduces chronic inflammation in your body. As a result, it may also reduce the risk of chronic disorders and disease, including diabetes, heart disease, metabolic problems, obesity, hormonal issues, infertility, autoimmune diseases, and cancer. [12] [13] [14]
Improves your relationship with food
A common problem in our modern world is eating without thinking, eating in response to emotions, eating large amounts at once, eating more than is necessary, and having a strong desire for unhealthy, sugary junk food. When you start intermittent fasting, you may realize that you no longer need to use food as a way to cope with boredom, stress, or other emotions. Fasting may be beneficial in treating food addictions and resetting your neurochemistry. IF focuses on helping people become more mindful when it comes to food.
Boosts Human Growth Hormone
A recent study of 200 participants showed that fasting for a single twenty-four-hour period increased HGH by 2000% for men, and 1300% in women HGH is essential for building, maintaining, and repairing healthy tissue in the brain, bones, and other organs, while speeding up healing after injury and repairing muscle tissue after exercise. HGH builds muscle mass, boosts metabolism, and burns fat. As you age, your levels of human growth hormone (HGH) naturally start to decline. This makes it even more important to take dietary steps to maintain and increase your HGH levels.
HGH can make your skin look younger by reducing sagging and wrinkles. [15] [16] [17] [18]
Increases BDNF, “Miracle-Gro for your brain”
Increased BDNF levels have been linked with better cognitive function and a reduction in age-related decline in brain function Brain-Derived Neurotrophic Factor (BDNF) is a naturally occurring growth hormone that is responsible for neurogenesis (the creation of new neurons). increased BDNF levels have been linked with better cognitive function and a reduction in age-related decline in brain function. That’s why Harvard Neuropsychiatrist, John J. John Ratey, a psychologist, believes that intermittent fasting can have a major impact on the brain, improving mood, cognitive ability, productivity, and memory while decreasing the risk of neurodegenerative diseases.
The reason fasting increases BDNF is not fully understood but researchers believe it is because BDNF helps to create new neural networks quickly. A thought, memory, or skill is formed when nerve cells in the brain fire together to form a network. We quickly form these networks in emergencies when we're put into fight or flight mode. We are in a state of controlled threat when we are fasting. A moderate amount of stress that increases stem cell production, HGG, and autophagy is probably also responsible for increased BDNF levels.
Intermittent Fasting May Affect Men and Women Differently
Although both men and women can benefit from intermittent fasting, the ways in which it affects them may be different. The discrepancies may be the result of hormonal differences. In addition to affecting insulin, norepinephrine, and HGH levels, intermittent fasting may have specific effects on female sex and hunger hormones.
Intermittent Fasting and Reproductive Hormones in Women
Women are more sensitive than men to calorie restriction and restrictive, low-calorie diets. Calorie restriction makes changes to the hypothalamus and the hormones that control it, like GnRH. This text is discussing the role of GnRH in relation to LH and FSH. GnRH is responsible for releasing these two reproductive hormones, which are important for fertility. If these hormones are disrupted, it can cause problems like irregular periods, not getting periods, infertility, small ovaries, and weak bones. [19] [20] [21]
Intermittent Fasting and Disordered Eating in Women
Intermittent fasting can interfere with the way ghrelin and leptin signal hunger and satiety. If your hormones are off, you may find yourself wanting food more, feeling hungrier, and not feeling satisfied after eating. There is a greater likelihood of women developing disordered eating habits, emotional eating habits, and eating disorders such as anorexia, bulimia, and binge eating.
Before starting an intermittent fasting protocol, it is important to talk with your healthcare provider if you have recovered from an eating disorder. If you have an eating disorder, we do not suggest intermittent fasting. [22] [23]
Intermittent Fasting and Insulin Sensitivity in Women
Insulin sensitivity may not be increased for all women who intermittent fast.
A recent study found that obese and overweight women whoul intermittently fasting saw a 29% drop in insulin levels and a 19% decrease in insulin resistance. A review published in 2014 found that intermittent fasting may help to lower insulin levels by 20 to 30% and blood sugar levels by 3 to 6% in those with prediabetes. [24] [25]
A study published in Obesity Research in 2005 found that alternate-day fasting for 22 days made blood sugar worse in non-obese women. But in men, it did not. Intermittent fasting may improve insulin sensitivity in women with insulin resistance, prediabetes, and diabetes. However, women without insulin resistance may experience hypoglycemic stress.
Even though there are some differences between how men and women process food, intermittent fasting can still be beneficial for women. Women can still experience the benefits of intermittent fasting. However, it's likely that women will benefit from different intermittent fasting strategies than men.
