Nutrition Q+A

Our health and nutrition advisor, Nicole, is tackling the food questions you crave answers to. Nicole is a Registered Dietitian and Certified Nutrition Support Specialist who practices in the inpatient and the outpatient setting. She has years of experience in the prevention and treatment of chronic disease. In the outpatient setting, she works with patients one-on-one and applies evidence-based practices to help clients achieve longevity and health goals unique to their individual lifestyles. She’s excited to share her answers to your top nutrition questions!

What is nutritional ketosis and how can I reach it?

Nutritional ketosis is a metabolic state in which your liver produces ketone bodies within a certain measurable output, generally 0.5–3 millimolar (mM). When thinking about energy that our body and cells use, the most common substrate needed is glucose. We get glucose from the carbohydrates and sugar we consume in food, but also from glycogen stores and proteins/fats in our bodies that can be converted to glucose.

The main component of a ketogenic diet is carbohydrate restriction. Reducing the carbohydrates that we eat reduces the amount of glucose available for energy production. Once glucose levels are low, our bodies then tap into our glycogen—our bodily stores of glucose—to break down and use for energy. Depending on various factors such as physical activity and baseline glycogen stores, liver glycogen will usually be significantly depleted between 24–72 hours. At this point, we need another energy source, so our liver starts making ketone bodies from fat or protein that we eat or from bodily stores.

A diet consisting of 20–50 gm carbohydrates (depending on the person and various factors such as physical activity levels and carb timing), moderate protein intake, and ad libitum fat will usually produce nutritional ketosis, as well as provide nutrients the body needs to fuel itself, without starving the body and losing valuable muscle stores.

I abide by the coffee and water lifestyle while fasting outside of my eating window, but I haven’t been able to find solid information on supplements and fasting. I assume the body will start metabolizing if vitamins, fatty acids, fish oil, etc. are introduced. Will supplements break a fast? Are there alternatives that will not break a fast if nutritional supplements will?

Arguments can go both ways on this one, and there may not be a single definitive answer—similar to the coffee debate. Some argue that anything breaks a fast, while others say only significant kilocalories (kcal) count. The purpose of your fast likely matters most. Are you fasting to have absolutely zero digestion occur, or are you trying to stimulate other functions such as autophagy or low insulin levels? These are things to consider when trying to answer this question.

If autophagy is your goal, then protein supplements and BCAAs will break your fast. When you fast, growth pathways like IGF-1 and MTOR are suppressed, which is necessary for autophagy to occur. If you consume protein, specifically BCAAs, during your fast you will stimulate these pathways.

If zero digestion is your goal, fish oil and other fat-based supplements likely contain an impactful amount of kcal. Therefore, if you’re practicing time-restricted feeding, try to keep all supplements within your feeding window. If you are doing a prolonged or multi-day fast, speak with your healthcare provider about which supplements are necessary for you to continue vs which can be removed during your fast. For example, most people can skip their fish oil supplements for five days without issue.

Electrolytes are likely fine regardless of your fasting goal and are generally considered to not disrupt the fasting state. In fact, for prolonged fasts, electrolyte supplementation is likely necessary.

What are the best foods to eat to prepare for and break a fast when on a Keto diet?

By being on a keto diet prior to a fast, you’re already on the right track. Going in fat-adapted and in a state of nutritional ketosis will make the transition into a fast easier. You could also consider shortening your feeding window ~one week prior to the fast to help prepare your body. Keep foods clean prior to a fast. A few days before the fast consider limiting foods to low-carb, non-starchy vegetables (lettuce, celery, cucumber, cauliflower, mushrooms, radish, etc.), healthy fats (olive oil, olives, avocado oil, macadamia nuts), and protein. Consider limiting or removing dairy if possible, and avoid fruit and higher-carb vegetables. This helps keep insulin levels low and ramps up ketosis going into a fast.

We recently shared a blog post on how to break a fast. Take a look for more detailed information. In general, break a fast slowly, especially if it is a long fast. Consider eating about ½ the kcal you normally would on day one, and then transition to a regular eating pattern from there. In addition to that, having a small portion of protein for your first meal such as eggs or chicken can be a good option, as they provide essential amino acids to help rebuild and repair the body. When you fast, growth pathways such as IGF-1 and mTOR are suppressed. Amino acids stimulate both of these, so once you reintroduce amino acids from protein sources post fast, you activate this beneficial growth period. Carbs also allow IGF-1 to be more bioavailable, so a small amount of carbs would be beneficial if it fits within your keto diet.

An example of your first meals post-fasting could be:

Lunch: 1 cup 2% or whole milk grass-fed, organic plain yogurt, ¼ cup raspberries, 1 hardboiled egg

Snack: small handful of almonds

Dinner: 3–5 oz. salmon with non-starchy vegetables sautéed in avocado oil

How can I get all of the nutrients I need when doing OMAD?

Variety in your diet is important to get all the vitamins and nutrients needed for your body to run optimally. OMAD does pose a challenge to this, but some strategies can help optimize nutrient intake.

Each day, mix up your meal to get in the most variety. Rotate different proteins such as salmon, organic chicken, and grass-fed beef, various vegetables — eat the rainbow—and different fat sources such as almonds, avocados, olives, and olive oil. Different foods contain variable levels of macro and micronutrients. Switching up these foods daily will help increase the chances you are getting each of these nutrients.

In addition to mixing up your meals, choosing nutrient-dense foods will help you get more bang for your buck. Some examples of these food include liver, eggs, seaweed, salmon, sardines with bones, oysters, kale, almonds, blueberries, beef, broccoli, and avocado.

What supplements should I use when fasting?

For most people who fast, sodium becomes an important nutrient to supplement with, especially for those on water only fasts and prolonged fasts. When nutrients, especially carbohydrates, are removed or drastically reduced from our body, our kidneys switch from retaining sodium to increasing sodium excretion in an effort to preserve potassium. In most cases, that lost sodium will need to be replenished. Sea salt is one option to supplement sodium, as well as bouillon which is another common choice.

During the increased osmotic losses during a fast, more water and magnesium are lost as well. Therefore, magnesium should also be supplemented during a fast. A slow absorbing formula such as SlowMag will work best and will be easiest on the GI system. Avoid magnesium oxide supplements while on a prolonged fast since that can lead to excessive loose stools and additional nutrient losses.

That being said, as is often the case with fasting, it’s always best to consult with your doctor on whether it is appropriate to fast and the supplements you may need to take on an individual basis, including sodium and magnesium. Some health conditions, such as hypertension, renal disease, or congestive heart failure, may not need supplementation the same as others do. In summary, always check with your healthcare practitioner first!

Is there an ideal time of day to eat your meals?

Recent studies have shown that feeding early in the day can provide more metabolic benefits. One study showed that pre-diabetic men who consumed their food within a six hour feeding window and had their last meal before 3pm for five weeks improved insulin sensitivity, blood pressure, oxidative stress, and appetite. Eating early aligns better with your circadian rhythm, which can be one proposed hypothesis for the cardiometabolic effects seen with this study. If insulin sensitivity decreases over the course of a day, the earlier you can feed, the less of a glycemic and insulin response there will be as compared to eating later in the day.

Should I eat raw, steamed, or cooked veggies?

It is likely best to consume a mix of both raw and cooked vegetables.

In some cases, cooking can destroy nutrients such as antioxidants and increase the amount of oxidized fats (if using fat with your vegetables) and carcinogens depending on the cooking method and duration used. However, cooking has its benefits, such as reducing exposure to foodborne pathogens and making nutrients more bioavailable. One example is lycopene, which is abundant in tomatoes. Cooked tomatoes produce higher amounts of lycopene compared to raw tomatoes.

The cooking method matters too. Charbroiling or grilling your vegetables can produce potentially harmful compounds, especially if the food is burned. Boiling your vegetables can leach out vitamins and minerals into the water, so unless you’re consuming the cooking water with the vegetables, you may be losing some nutrients. Steaming and sautéing at low to moderate heat with oils that have a high smoke point is the best option. Steaming uses little water, so less nutrients are leached, and cook time is usually quick — AKA long enough to make nutrients bioavailable, but not so long that you begin destroying significant amounts of nutrients. Sautéing is another good option. Since the cook time is also fast, you don’t lose nutrients through water, and in some cases, the added fat helps increase bioavailability as well.

How bad is it to end a fast with carbs and/or sugar?

Ending a fast with high-quality carbohydrates is fine, as well as some natural sugars if they fall within your post-fast meal plan. High-quality carbohydrates are generally those that are digested and absorbed slowly (i.e., low glycemic), are from whole food sources, and are coupled with other nutrients such as fiber, vitamins, and minerals. Natural sugars come from whole grains, vegetables, dairy products, and fruit. If you plan on going into a strict ketogenic diet post-fast, then you will want to consider limiting the quantity of these items in order to stay in ketosis.

Consuming low quality carbs — those that are highly processed, have low nutrient density, and are usually riddled with unhealthy fats and added sugars—is not a good idea. This can lead to the blood sugar/insulin rollercoaster, sugar cravings, and potentially undo the good benefits you received from fasting if consumed in excess.

Are there any foods that should be avoided at all costs from a health/nutrition perspective?

Most foods can be incorporated into a healthy diet, however, there are three categories of food that the majority of us are better avoiding:

Added Sugars: A small amount of natural sugar is normally fine in a diet, and our ancestors have consumed it for many years without issue. However, the main problem we see today is the sheer quantity of sugar in our products—the majority coming from highly processed sources. Processed sugars have been shown to trigger the growth of harmful gut bacteria, impair immune function, increase risk of cardiovascular disease, have negative impacts on the brain, and have a potential link to cancer. Any products that have sucrose, high fructose corn syrup, agave, and other sugar derivates are best to avoid.

Industrialized Oils: Industrialized high omega 6 oils are processed oils extracted from soybeans, corn, grapeseed, cottonseed, and safflower seeds. These were not part of our ancestral diets and were not introduced into our food sources until the early 1900s. The two main issues with these oils are that they are highly processed and that most of them contain high amounts of omega 6 fatty acids.

Processing oils creates potentially harmful compounds and increases the chemicals that are added to the product. High heats that are used to extract the oils oxidize unsaturated fatty acids, creating harmful byproducts, and hexane and other chemicals are added in the processing to create the final product.

Omega 6 fatty acids are an essential fat. However, Americans today are consuming much more than they actually need. In addition to that, many people do not consume enough omega 3 fatty acids, which are essential to balance out the omega 6’s. Omega 6 fatty acids in excess and a high omega 6 to omega 3 ratio can contribute to chronic disease such as cardiovascular disease, cancer, and inflammatory issues to name a few.

Packaged/Processed Foods: The main reason most packaged and processed foods should be avoided is because they usually contain the items mentioned above (added sugars and industrialized oil). Added sugars and industrialized oils are not only harmful for the reasons I’ve listed, but other studies have shown that the combination of the two can also contribute to health issues such as insulin resistance and NAFLD. In addition, packaged and processed foods are usually low or void of vitamins, minerals, and other healthy nutrients and might take the place of other foods such as vegetables and healthy fats that are more nutrient dense.

Should I avoid dairy during feeding windows when practicing fasting?

The answer to this question is…it depends! Dairy can be a good addition to a diet depending on the individual’s response to it. Organic and grass-fed products should be chosen over conventional dairy products to increase the beneficial fat content and decrease exposure to harmful byproducts from the questionable food, hormones, and medications that conventionally raised animals are given. Organic, grass-fed dairy can be a great source of protein and fat, and micronutrients such as calcium, potassium, phosphorus, and probiotics if consuming fermented dairy products. However, dairy isn’t for everyone. Allergy to dairy proteins — casein and whey—is fairly common yet mostly undiagnosed, and in certain individuals, can contribute to low levels of inflammation. In other individuals, dairy can cause side effects such as acne, skin issues, and gut intolerance—in which case, it’s better to avoid.

Determine your own tolerance to dairy, ideally with your healthcare provider. If you don’t have any issues consuming it, it should be fine to keep in your diet. Just choose organic and grass-fed whenever possible to ensure the best quality nutrients.

Now that you’ve got the nutrition info you need, it’s time to start fueling your fasts! Share your favorite feeding window foods with us this week on TwitterInstagram, and Facebook using #FeedingWithZero.

Posted in Q+A's


  • So many keto friendly foods and recipes contain heavy creams, cream cheese and other cheeses.
    If one were to consider avoiding dairy, the ketogenic diet becomes even more restrictive.
    Any thoughts and
    comments are appreciated.

    • I red a lot about fasting, and i know for sure that besides water it’s not allowed to drink or eat anything else👍👍

      • It depends what your purpose of fasting.
        Gut rest restricts black coffee but ketones favour it(some data suggests).

  • Hey Zero team, could you please post information on how to combine fasts and regular strength/weight workouts correctly, so to keep growing muscle mass? What could be feasible fast regimes and diet options? Is gaining muscles possible at all while following intermittent fasting regime? If not, how to at least maintain the muscle volume? Thank you!

  • Hi! I’d love an article about artificial sweeteners- whether or not they break a fast, their effects on the body, different types, etc. It’s something I haven’t had a lot of luck researching.

    • I fast and have IBS, and I have seen a decrease in my ibs symptoms while fasting. I still avoid my triggers when I do eat but I really think fasting has helped. I do have to follow a low fodmap diet.

  • I also echo Irina’s question. I powerlift and sometimes can’t do so until evening. Wondering how to time workouts and meals.

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