How are blood sugar, cholesterol & the HPA axis involved?
Here’s the good news:
Intermittent fasting is normal part of our genetic and evolutionary history. Times of feast and famine are a part of many if not all cultures. It’s a hormetic stressor, meaning it promotes cellular repair. As a tool for weight, it promotes a metabolic shift that preserves muscle mass. (1) For those with moderate blood sugar imbalances, intermittent fasting may help regulate insulin levels.
Intermittent fasting has shown to reduce cholesterol by 20 per cent. This research indicates a decrease in the ‘bad’ LDL’s while maintaining the ‘good’ HDL’s. Triglycerides decreased up to 32%. Triglycerides are associated with cardiovascular disease and diabetes (2,3,4).
Another study showed increased motor coordination, brain health and oxidative stress in an aging population. On that note inflammation and disease associated with neuroinflammation were also positively affected. These include depression, other mood disorders and Alzheimer’s. (5,6,7) I’m imagining how society would change if most elders were free of disease associated with chronic inflammation. What if we could age with sharp minds, stable moods and free of pain?
When to be cautious?
With all this evidence why am I often cautioning patients and instead encouraging eating at regular times? People tend to miss meals when stress is high or eat at times that undermine healthy organ and metabolic function. There are a few specific situations where intermittent fasting is not advisable. For those with HPA axis dysregulation the stress of fasting can worsen their symptoms. These include the inability to fall or stay asleep, afternoon crashes, poor stress response and slow exercise recovery time. Another endocrine disorder where caution is advised where thyroid issues are suspected . Low glucose levels exacerbate thyroid disease because a constant source is required for the conversion of T4 to T3. Functional tests are available to help assess if you are at risk for this.
Pregnancy is another time to avoid intermittent fasting for obvious reasons. Anyone trying to maximize fertility or with hormone imbalances may want to avoid fasting. However if blood sugar or excess weight are contributing factors intermittent fasting may be helpful. Working with a clinician is a good idea to help assess a treatment plan. Keep in mind that more severe insulin resistance does occur in otherwise healthy individuals and this would be another time to avoid fasting.
Children and teenagers do not benefit from fasting as it can cause problems in the same way fasting during pregnancy is not wise. Both can cause epigenetic stressors leading to insulin or leptin resistance later in life. The young one’s system gears up for weight gain to protect from starvation and times of famine.
Anyone with a history of disordered eating needs to be very cautious and not engage in fasting without adequate support. Orthorexia is a term that refers to obsessive behaviour around food with a tendency to become addicted to special diets. If I hear a patient refer to certain foods as bad or even as poison.
Finally if you experience stomach or abdominal pain upon fasting there may be an infection of pathogenic bacteria like heliopylori or other dysbiosis present that needs to be addressed first. Testing for these is available and may reveal important or even life changing information.
How to do it?
If you fall don’t fall into any of the above categories its best to try intermittent fasting when overall stress is low and when your life makes space for it. Perhaps you are sleeping well and there are no big life changes happening. If you are moving, ending a relationship or having a baby it’s definitely good to wait.
Otherwise here are some approaches to intermittent fasting. Many start by skipping one meal a day or extending the duration of the overnight fast to anywhere from 12 to 20 hours. Others prefer whole-day fasts that involving fasting for 24 to 30 hours, once a week or twice a month. Most of the research on intermittent fasting uses alternate-day fasting, where participants fast for 24 hours every other day, alternating days of eating without restrictions.