Happy Monday! I am so delighted you enjoyed last week’s conversation about protein needs for women with Anthea Levi, RD. There are so many opinions out there and I understand why it can be confusing to know what to eat and how to stay healthy. Another subject that I know women find overwhelming is what to think about intermittent fasting. I asked my friend and well-respected RD, Keri Glassman, some burning questions I had about IF. Keri is a go-to source for me for science-backed information.
1. What is IF and why has it become such a buzz word in the diet world?
Intermittent fasting is a broad term that covers a pattern of eating that involves a set amount of time where you don’t eat (or eat an incredibly restricted number of calories), followed by one in which you do. The most popular version involves fitting all of your daily food consumption into an eight-hour window, followed by 16 hours of fasting. For example, you could eat between 10 a.m. and 6 p.m. every day and fast between 6 p.m. and 10 a.m. There’s also the 5:2 diet in which you split your week into five days of eating whenever you want and two days where you seriously restrict your calories—500 for women, 600 for men. While fasting may seem extreme and irregular, proponents argue that humans actually ate this way for most of history, since hunters-gatherers ate when food was available, not at set mealtimes. Plus, fasting is an age-old part of nearly every religious tradition. Reason why it has become popular (in 2019 it was the top Google search term in its category) is first, it does help lose weight. Also, social media and reality tv stars touting their specific regimens has led to the rise in popularity of this style of diet.
2. What are the different types of IF methods?
In addition to the 16:8 and 5:2 versions of IF mentioned above there are also these versions: 14:10 which is the same as the 16:8 plan with a shorter fasting period. This is often more doable for people. Alternate Day fasting is where you eat “normally” for one day and then severely restrict calories the next by drinking only no calorie beverages or eating less than 500 calories. This is my least favorite version of IF. Warrior Diet, where you eat raw fruits and veggies during the day and choose a short window of time in the evening where you eat a meal of whatever you want. Also, not a fan of this one.
3. There is circulating information regarding fasting negatively impacting female hormones - what is the science/what are your thoughts on this?
Some studies have shown benefits to IF including weight loss, improved insulin sensitivity, cognitive function, and even reduced risk of cancer. There is a big but here…because fasting affects our hormones and because female hormones are continually fluctuating and interrelated, it is super important to be aware of how you respond to IF and for many women it is not the right choice. Our bodies are built for reproduction. Extended periods of time without food may tell your body to “stop and slow down” on those hormones that play a role in reproduction (estrogen and progesterone). Your body doesn’t want to get pregnant and carry a baby when it perceives you to not be eating adequate calories. If you notice your period changes with IF, you should probably not be doing it. This is also why women who are in the perimenopausal stage of life may not want to do IF. Hormones are shifting a lot during this time, progesterone and estrogen are decreasing. IF may further exacerbate this and make a woman sleep worse, irritable and even gain weight. Remember, progesterone and estrogen play many important roles—they are not there simply for reproduction. For example, progesterone helps to metabolize macronutrients and aid in blood sugar regulation. Also, depending upon how your body responds to stress, IF may not be for you. IF may be too much of a stressor and increase cortisol levels which is also not good for weight loss. As women’s hormones are shifting during perimenopause and progesterone and estrogen are decreasing, women are also already more sensitive to stress.
4. What are your general thoughts on utilizing IF as a weight-loss strategy for women?
I’m not a fan for most women for all of the above reasons. There are certain women who it may work well for. You really have to track how you feel, how you are sleeping, what your mood is like and what your menstrual cycle is like as well. Also, it may be helpful for women with PCOS. Like most things with diet, it is very individual and if you choose to give it a go, you should probably work with an RD or nutrition coach.
5. What else can IF help with regarding women’s health?
I mentioned the biggest benefits above—weight loss, improved insulin sensitivity, cognitive function, and even reduced risk of cancer—but here is some more…As far as weight loss goes it’s important to remember that most studies have found that the benefits are most likely due to calorie restriction. When you limit the amount of time you have to eat, you limit the amount of calories you consume. Fasting may lead to improvements in pancreatic B-cell function and the regulation of the circadian rhythm, which promotes better glucose tolerance. In a randomized controlled study of more than 100 overweight or obese women, six months of intermittent fasting reduced insulin levels by 29% and insulin resistance by 19%. Reductions in fasting insulin and insulin resistance were modest in both the intermittent fasting and continuous energy restriction groups, but greater in the intermittent fasting subjects. Another study on non-obese subjects also found that fasting decreased insulin levels and increased fat oxidation—the process that breaks down fat during energy restriction or exercise. Studies have found that fasting may improve depression and stress levels, and encourage overall positive psychological shifts. Fasting has also been shown to increase BDNF expression in rats, a protein that serves as a sort of fertilizer or “miracle-grow” for the brain. There are no studies on how fasting affects the human brain yet, but one of the most common things people report while fasting is increased mental clarity. There is also research emerging that shows that fasting may be beneficial for reducing risk factors for cancer.
6. What is the best meal to break a fast with?
A whole food nutrient-dense meal with a balanced proportion of macronutrients.
7. What is the ideal eating window for women?
There is no “perfect window”. It is really more about what time works for you and your lifestyle. Ideally it will be one that aligns your meal times with your body’s natural circadian rhythm. So for example, you finish dinner at 7 pm, go to bed at 10pm and wake up and eat breakfast at 7am. This would be considered a 12:12 schedule. Some may call this IF, I think of it more simply as the correct way of eating for most people. It gives your body enough time to reap the benefits of IF without causing any harm. Your digestive system has time to rest and you skip that after dinner and late night eating. You also benefit from breakfast and setting the tone for a healthy day of eating.
8. What are the downsides or challenges with IF?
The downsides are the hormonal implications discussed above, as well as it can actually cause many people to make worse food decisions and eat a less healthy diet. For example, someone who always ate a healthy-ish breakfast of say, oatmeal, nuts and fruit and lunch of a salad with protein, may end up skipping breakfast (to adhere to the fasting window) and then eat two slices of pizza at lunch because she is in a mindset of eating “whatever she wants” during the fasting window and she is starving when the clock strikes the end of the fasting window.
9. Are there any other things we should consider before implementing IF into our lives?
Is this something that feels right to you? Is it going to be doable for you? Will it make healthy eating easier or harder for you?Have you always been a breakfast person? Do you think this will cause you to overeat? Does it feel like it may stress your body? Most people, when they really think about it, know what will work for them. This is also a good conversation to have with your MD, RD or nutrition coach.
10. Do you recommend IF to your female clients? Who would you not recommend fasting for?
I do not recommend it to athletes, people with DM, women with a history of an eating disorder, teenage girls, pregnant women, women who are breastfeeding and most women in perimenopause. Also, I’d say any highly stressed woman I would not recommend IF.
If you learned something from my discussion with Keri, check out her website and her instagram.
My newsletter is a sponsor-free zone and is fully supported by readers. Consider being a paid subscriber to get Even More Musings! Today I am sharing an easy, new favorite dinner, which is a tweak of my chicken and rice skillets! Tex-Mex Skillet Chicken and Rice is a great one-pan meal and can be adapted for vegan diets as well. Enjoy!
Keep reading with a 7-day free trial
Subscribe to Pamela’s Monday Musings to keep reading this post and get 7 days of free access to the full post archives.