There is increasing evidence from recent human and animal studies that intermittent fasting — refraining from food or caloric beverages for at least 12 hours a day, several days a week — reduces the risks of cardiovascular disease, dementia and cancer. Those benefits are well-documented in the hyperlinked articles, so I won’t repeat them here. Yet many nutritionists hold that skipping breakfast or other meals and snacks can lead to weight gain and metabolic imbalance. Several recent articles have suggested that IF and breakfast skipping is a particularly bad idea for women. Much to my chagrin, this view been even embraced recently by a number of ‘Paleo’ advocates whom I respect, such as Chris Kresser and Mark Sisson.
In this post I’d like to address three main objections that have been raised against skipping breakfast and other forms of intermittent fasting:
- It spurs hunger cravings, leading to compensatory overeating and obesity
- It causes cardiovascular disease and metabolic dysregulation of blood glucose and hormone levels
- It’s bad for women, leading to hormone imbalance, disrupted menstrual cycle, and heightened stress response
I believe these concerns with breakfast skipping are overblown, based on an incorrect interpretation of a few animal and human studies, and flawed personal implementation. To the contrary, adaptation to meal skipping can actually help boost stress tolerance and improve blood sugar control. If practiced correctly, intermittent fasting (IF) can actually be a powerful tool to overcome hypoglycemic symptoms, and regain control over a harried lifestyle. And it can be particularly useful for women who are struggling with cravings, weight management and stress management.
Opposition to intermittent fasting arises from both published research and anecdotal reports. I’d like to address both in this post. I’ll first point out some significant flaws in the interpretation of several recent studies purporting to show negative effects of reduced meal frequency on women and other groups. And I’ll end by pointing out how to avoid common mistakes made by many who try intermittent fasting find it to be unpleasant and unsustainable.
Approached correctly, IF can provide major health benefits for most us.
There’s a surprisingly simple but little-known technique for measuring your in-the-moment ability to handle physical, mental and emotional stress. Some of us have a higher level of “adaptive reserves” than others. And for all of us, these adaptive reserves increase or decrease throughout the day and over days or weeks. You might have a rough, intuitive sense of when you are more resilient to stress, and when you are weak or more vulnerable. There is no shortage of advice on the Internet about “stress management”, fitness and diet. In general, sleep, physical activity and a nutritious diet build adaptive reserves, while these reserves are easily depleted by chronic stressors like worry or overwork.
But how do you know what really works to improve your resilience and resistance to physical and psychic stressors? How can you learn what diet, exercise, and activities actually work for YOU — not just what researchers, health professionals, bloggers or your friends claim should work?
What if I told you that there is a reasonably objective metric for your overall adaptive reserves and a simple, inexpensive, and noninvasive way to measure your adaptive reserves throughout the day.
The metric is called heart rate variability, or HRV. It can be measured in less than a minute, using an inexpensive chest strap or finger sensor, and any of several smart phone apps that can be downloaded for a few dollars. Based on a review of numerous studies and extensive personal experimentation, I’ve learned some surprising things about what tends to raise or lower HRV. And I’ve found one few amazingly quick, effective, and to boost a low HRV and keep it up, with real impact on adaptive reserves. (For the impatient, scroll to bottom of this post and read Recommendation #1).
How much weight lifting or other exercise is optimal for fitness? What is the right amount of carbohydrate restriction or fasting for sustained weight loss and health? What level of exposure to allergens will reduce allergies? How many hours of sun tanning is healthy? How frequently should plus lenses be worn to reduce myopia? Do I need to take cold showers every day to get their benefit? How much stress is enough — and how much is too much?
Many of the questions I get on this website and the forums are of this type. People understand the general concept of hormesis, namely that exposure to controlled amounts of stress can be beneficial, because it elicits beneficial adaptive responses in the organism. They understand that weight lifting builds muscles, and that intermittent fasting and calorie reduction can be healthful. But too much of any stressor — weight lifting, caloric restriction, sunlight, allergens — can have adverse consequences. With hormesis, it seems, the Goldilocks principle applies: to get a benefit, the level of stress must be “just right”. And because it’s so easy to veer into overload, many people seek to avoid even mild stress: Avoid allergens. Cover up with sunscreen. Eat frequent small meals. Don’t exert yourself. But if you choose this path, you forgo the possible hormetic benefits.
So how do you determine the optimum level and frequency of exposure to a stress? And how much rest or recovery between exposures is optimal? Read More