The Whys and Hows of a Safe Fast

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We want to acknowledge that here in the U.S., one in eight households (12.8 percent) experience food insecurity, or lack of access to an affordable, nutritious diet, and that a discussion of intentional fasting is a privileged discussion. Please consider signing up with Share Our Strength, a highly efficient organization with a mission to end hunger and poverty in the U.S. and abroad. Donate to their No Kid Hungry campaign here.

Fasting is all the rage these days. It seems like everyone doing it, but often for poorly understood reasons, and in inappropriate ways. There are downsides to fasting, including losing lean body tissue that can be very difficult to regain. Fasting can also contribute to disordered eating, weight loss obsession, low blood sugar, and elevated stress hormones in the female populations we work with.

However, we have long been proponents of fasting, including intermittent fasting, because truth be told, the health benefits can’t be beat. Like so many things in life and health, two things can be true at once. Fasting can be dangerous and beneficial, and the devil is in the details. Here we discuss the benefits and dangers of fasting, and how to do it safely.

Benefits of fasting

Intentionally taking a break from food (fasting), when done safely, can provide a host of benefits to your health and increase your longevity. Fasting is one of the best ways to:

  • Control calories and lose weight – People often think that intermittent fasting magically causes weight loss. It can cause weight loss but it’s not magic. Research shows that intermittent fasting works for weight loss simply because people consume fewer calories due to a smaller eating window. Not magic. It’s just fewer calories. But, it’s easier for some people than counting calories.
  • Lower insulin and improve cardiometabolic health – Not only can fasting lower blood pressure and oxidative stress, it can also lower markers associated with insulin resistance, such as hemoglobin A-1 C, glucose, insulin, and triglycerides. If you’re interested in fasting your way out of type two diabetes, read Jason Fung’s work.
  • Reduce inflammation and autoimmune cytokines – Fasting can lower the proinflammatory cytokines IL-1β, IL-6, and tumor necrosis factor, as well as the inflammatory markers homocysteine and C-reactive protein. It can be a fast way (pun intended) to stop an autoimmune process.
  • Promote autophagy – This is when your cells get busy cleaning out damaged parts and invading pathogens. It’s clear that fasting elicits autophagy, although it’s unclear when this happens – some say 24 to 36 hours of fasting is needed, so a 12-16 hour overnight fast may not cut it. Promoting autophagy can help reboot your mitochondria, prevent cancer and dementia, and slow the aging process.

Dangers of fasting

Fasting is not for everyone. Fasting is NOT for:

  • Children and adolescents
  • Pregnant and breastfeeding women
  • Underweight people
  • Those with active eating disorders
  • Anyone who feels like their mental health tanks with food restriction!

Populations that should be very careful about fasting include:

  • Lean people – If you don’t have fat to lose, fasting puts you at risk of losing important lean body mass like muscle and bone tissue.
  • Menopausal women – The potential loss of muscle and lean body mass is much harder to overcome post-menopause.
  • Stressed-out folks – Fasting can increase stress hormones, so people who are already stressed should take care. High stress does not mix well with fasting.
  • People with low or unstable blood sugar – Fasting may drop blood sugar too low and cause increased stress. If you get cranky, irritable, or shaky when you’re fasting, that’s a red flag!

“Intermittent fasting,” which is simply extending your overnight fast to 14-16 hours, is generally safe. You are unlikely to break down lean body mass during this period of time. However most intermittent fasters push breakfast later, and this is not the best way to benefit from the fast. The benefits are greater if you eat a protein-strong breakfast within two hours after you wake up and then stop eating earlier in the day. For example, if you get up at 7 AM, plan to eat at least 30 g of protein with breakfast by 9 AM, and then stop eating by 5 to 7 PM in order to get a 12 to 16-hour overnight fast.

How to fast safely

Extending your overnight fast up to 14 to 16 hours will get benefits without the danger of losing lean body mass. If you’re like the majority of adults in the US and have some insulin resistance and excess weight, this type of intermittent fasting may help you lose weight and improve insulin sensitivity. However, it’s less likely to get the deeper benefits that you get from a longer fast – decreasing inflammation and autoimmune cytokines, preventing cancer, and increasing longevity.

So how do you get the benefits of a longer fast (2-5 days) without being insanely hungry or losing muscle mass?

This is where Professor Valter Longo’s work and the Fasting Mimicking Diet (FMD) come in. Longo, author of The Longevity Diet, engineered the FMD as a five-day fast that includes specific small amounts of plant-based foods that prevent muscle loss while still allowing autophagy. This means you can eat a reduced-calorie diet for five days, not suffer too much from hunger, and get all the benefits of an extended fast – without losing lean body tissue. This is extremely important, especially for women over 40, when hormonal changes and aging make it more difficult to maintain muscle and bone mass.

The why and how of the FMD

Since the FMD is five days, we recommend it for people who want the deeper benefits of fasting beyond weight loss. It’s for those who want to promote autophagy, reduce inflammation, lower blood pressure, reverse type 2 diabetes and autoimmunity, and increase lifespan. It provides all the benefits of a water fast but without the dangers of losing lean body tissue. However, since it’s a low-calorie approach for five days, you will feel hungry. Generally, appetite suppression kicks in by the third day of the fast.

The easiest and most exact way to do an FMD is to purchase a ProLon® five-day meal kit designed by Longo. You can purchase a kit for $148 here with our discount:

Another way to do an FMD is to create a DIY version. In 1999 we created a DIY program called Fasting With Food® which provides a DIY approach to the FMD. We created this for these reasons:

  1. To provide a more economical way for people to do an FMD
  2. Freshly prepared food tastes better!
  3. People have food sensitivities and a DIY version allows for substitutions.
  4. For those following a Paleo diet, our DIY menus are Paleo-compliant.
DIY Fasting Mimicking Diet

How often can you do the FMD?

You may do the FMD once a month, but not more often. Some people do an FMD once a season, or every three months. Others do one per month until they reach their goals of reducing inflammation or reversing a condition. Check with your healthcare provider about what’s right for you. If you’re working on changing markers on bloodwork, we recommend testing after three months to gauge how your numbers are changing.

Our free FMD groups

We run free FMD Facebook groups (these do not include the cost of the Prolon® kit or the Fasting With Food® program) to provide motivation and support for those doing a five-day FMD. Contact us to get on the list for our next group.

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