Intermittent Fasting for Women; Is it a Good Idea?

Let’s talk weight loss, pregnancy, immunity and disorder eating behaviors

As you may know, Intermittent Fasting (IF)is a broad term that describes going for a period of time without eating. There are lots of different forms of intermittent fasting (16:8, 5:2, and OMAD, to name a few), but the intended benefits are generally the same across the board, including weight loss, increased energy, and improved mental clarity.
Although many people swear by intermittent fasting, there’s a gray area and conflicting opinions regarding whether intermittent fasting is safe for women.

When you fast, there is no glucose source coming from your diet, so your body kicks a back up mechanism into gear to regulate your blood sugar level and it releases cortisol. Fasting increases cortisol, especially when someone has already dysregulated blood sugar level, or is under stress.

Insulin is one of the hormones that regulate blood sugar. When fasting, insulin level lowers as it is normally released in the presence of food. This means that fasting works well when trying to increase insulin sensitivity, but there is a catch.
Most research has been done on men. When studies have included women, it has shown no difference in insulin sensitivity, unless the woman was already obese or insulin resistant. To make the matter worse, some studies have demonstrated that an extended period of fasting in healthy women can have the opposite effect and are detrimental for the blood glucose level.

On a more positive note, Intermittent fasting has been shown to

  • Reduce oxidative stress (which damages DNA)
  • Improve cardiovascular functions (lower cholesterol, increase metabolic rate, lower blood pressure)
  • Improve cognitive function and brain health
  • Improve immune system and longevity

Because it promotes autophagy, which is also called cellular cleaning, and apoptosis, which is also referred to as programmed cell death. By turning on these processes, our body goes through a thorough spring cleaning and clear all the “unproductive” and damaged cells, hence lowering inflammation. Autophagy already exists, and our body does it regularly, but this process is generally sped up in response to nutrient deprivation, and stress, which is why fasting works so well (on a side note, also exercising and infrared sauna support the clearing of damaged cells).

Fasting has also been shown to have several beneficial effects on metabolism that may lead to a reduced risk of cancer, which is characterized by uncontrolled growth of cells. Although human studies are needed, promising evidence from animal studies indicates that intermittent fasting may help prevent cancer. There is also some evidence on human cancer patients, showing that fasting reduced various side effects of chemotherapy.

Unfortunately, IF doesn’t work for everyone, and it depends on the individual and what is going on someone’s life.

As I said before, most of the studies that have proven the benefits of Intermittent fasting have been done on men.

But what about women? When is IF a bad idea?

At this point, we know for sure that certain groups of women definitely shouldn’t fast.

This includes anyone who:
• Is pregnant or breastfeeding
• Is underweight
• Has a history of disordered eating
• Is under a great deal of chronic stress
• Has other major medical issues, like diabetes or high blood pressure
• Is prone to anxiety
• Has gut issues and sleep disorders

One of the main issues is that women don’t eat enough in the “feeding window”, especially when Intermittent Fasting is treated more like a diet.
On that note, I would also like to add that people do IF to burn fat. It is true that when fasting, you burn fat as fuel, but that doesn’t mean body fat in all situations; sometimes, our body breaks down muscle tissue to increase the amount of glucose in the blood.

While following IF, women struggle to eat sufficient quantities of necessary nutrients. Most of the time, they don’t meet the caloric intake required by their bodies (and hormones) to function optimally.
This caloric restriction sends a message to the brain that there is a famine so that it stops communicating with the ovaries, it drops sex hormones production, and it can lead to a cascade of side effects such as amenorrhea, impaired fertility, poor memory and immune health, and low bone density.
Moreover, high cortisol levels can interfere with sleep quality, leading to mood disturbances, gut issues, and anxiety.

It is suggested to avoid intermittent fasting when suffering from Hypothalamic Amenorrhea, as the body needs to feel safe to ovulate. When recovering from HA, it is required to eat every 3 hours to prove the brain that there is no famine or threat to survival. Until then, it is almost impossible to restore a menstrual cycle.

It has also been noted that the cost of fasting doesn’t outweigh the benefits in women suffering from underactive thyroid and Hashimoto.
In this specific instance, the worst possible thing to do is to fast and follow a low-carb diet to lose weight. You can see short term benefits and put yourself in a worse position than when you started.
The body won’t let go of fat when it feels under threat (it automatically slows down the metabolic rate), and it’s suggested to work with your body instead of fooling it.

And what about pregnancy? Fasting promotes fat burning, but women in pregnancy are supposed to be creating and storing fat, not burning it. This could lead to an inadequate weight gain of the growing fetus and hormonal imbalances that could cause significant harm. Fasting can also create a brief time of hypoglycemia (very low blood sugar) while the body is trying to change from a glucose-burning state to a fat-burning state, which is bad for the fetus even if happening briefly.
Additionally, while fasting is good for the immune system in general, it lowers immune function for a period of time. And, as women who are pregnant have reduced immune function already, lowering it further is not a good idea.

Intermittent fasting is better to be also avoided when breastfeeding. IF restricts the amount of food (nutrients) and fluids for both mum and baby, and increased caloric intake and continuous fluids are needed to maintain a woman’s milk supply. In this case, IF can lead to dehydration, low energy levels, and reduced milk supply.

If you have decided to try IF no matter what, make sure you do it smartly and safely, by following the below tips:

• Start with a smaller fasting window, and work your way up
• Start with only two fasting days per week
• Avoid high-intensity exercise (including running and biking) on fasting days
• If you feel weak, tired stop fasting
• If you feel dizzy, cannot sleep, or are anxious, stop fasting
• If you lose your period, definitely stop fasting. It is not for you!
• Eat healthy, nutrient-dense foods during your feeding windows. Don’t satiate your hunger with pizzas and cupcakes only. On the same token, make sure to have balanced plates made of carbohydrates, fats, and protein
• Track your symptoms and how your body feels
• Talk to your doctor before starting IF

Claudia is a Qualified Nutrition & Dietetic Consultant (BHSC) specialised in hormonal balance, women’s health, and disorder eating behaviors. She sees clients online and in clinical practice; you can find more about her or the Hypothalamic Amenorrhea recovery program by following her on Instagram, Facebook, or by checking her website.

Qualified Holistic Nutritionist (BhS)- Disorder Eating/ Fertility/ Pregnancy/Postpartum. Mother. Coffee Drinker. FREEBIES:

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