Intermittent fasting, or IF, is not a diet, but a way of eating that involves cycling through fasting and eating windows. Relatively short fasting windows last anywhere from 12-24 hours and are interspersed with periods of regular, healthy eating.
So what’s “regular eating” while taking part in an intermittent fasting protocol? It takes simple common sense to understand the positive effects of IF may be negated if, during the eating window, you’re filling yourself with donuts, candy, and cake. But is there a best diet to go with intermittent fasting?
We explore several popular diets and their effect on your intermittent fasting protocol.
Intermittent Fasting and the Keto Diet
The Ketogenic Diet, or Keto Diet, is a low-carbohydrate and high-fat diet that has gained popularity for its influence on fat burning. The ketogenic diet and fasting are frequently done together. Properly executed, the ketogenic diet encourages a state of ketosis in the body, which is what happens when glucose is no longer available for energy, and the body turns to ketones and fat burning as an alternative fuel source.
The ketogenic diet is not new, yet in the past was used mainly as a medical diet for patients with epilepsy to reduce seizures. The anticonvulsant properties of the diet point to the effects of ketosis on the brain, which even healthy bodies may potentially benefit from.
While many partake in the keto diet with weight loss in mind, the ketogenic diet has been shown effective in boosting memory and preserving it well into old age, reducing inflammation in the brain, preventing the onset of Alzheimer’s disease and increasing the presence of mitochondria for optimum brain performance.
Ketogenic Diet How-Tos
To achieve a state of ketosis, it’s recommended to consume less than 25 grams of carbohydrates daily, and fuel instead with high-fat foods containing a small amount of protein. A typical ketogenic diet consists of 75% fat intake, 20% protein and just 5% carbohydrate.
A keto breakfast might include healthy fats such as avocado with a small portion of eggs for protein. A typical lunch or dinner on the ketogenic diet consists of a small grass-fed steak and large amounts of vegetables roasted in organic, grass-fed butter for a high-fat content.
Those on the keto diet avoid alcohol and sugary foods, including fruit. Beans and legumes, root vegetables, starches and grains are all off the list due to their high carbohydrate content.
Recommended foods include eggs, fatty meats and fish for protein, and organic, grass-fed butter and cream, cheese, nuts, avocados and healthy oils like coconut oil, avocado oil and extra virgin olive oil for fats.
The Ketogenic Diet and Fasting
Fasting on a ketogenic diet can boost both the effects of the fast and ketosis in the following ways:
- Intermittent fasting also promotes ketosis, so this process can be maximized and ketosis reached sooner by combining a ketogenic diet and an intermittent fast.
- Fat burning can increase when ketogenic meals are grouped together, thus forcing the body to burn its energy stores, rather than building them up throughout the day.
- Intermittent fasting promotes muscle building (primarily through growth hormone production), which can sometimes be difficult on a ketogenic diet due to the low intake of protein.
- Ketosis reduces hunger (by suppressing the hunger hormone ghrelin) which can make it easier to stick to your fast. Eating fat is also very satiating.
- Both intermittent fasting and keto help the body turn to fat as a source of energy. When used in conjunction, fat-burning benefits are maximized.
Intermittent Fasting and the Paleo Diet
Different from the ketogenic diet, the paleo diet is a method of eating that mimics how our ancestors might have eaten before the onset of agriculture. Healthy, whole foods are emphasized over-processed, farmed or manufactured foods. Whole nuts, berries, vegetables, meat, and fish are encouraged, while those on the paleo diet avoid grains, sugars, dairy products, rice, and beans.
The assumption behind the paleo diet is that our human genome largely developed in pre-agricultural times, and thus, even today, is best served by this way of eating. While there are paleo diet pros and cons, those on the paleo diet find they benefit from the removal of manufactured, processed and highly refined foods, which consist mostly of high sugar carbohydrates. Many turn to the paleo diet for weight loss, but there are other benefits as well.
The diet claims to improve gut health by avoiding gut-damaging grains, legumes, and dairy proteins and is recommended for those with irritable bowel disease, or IBD, and celiac disease. Studies show that a paleo style of eating lowers blood sugar and improves insulin sensitivity, reduces the presence of triglycerides (specific fats that may increase risk of heart disease and death) and reduces high blood pressure.
Paleo Diet How-Tos
What can you eat on the paleo diet? Also known as the caveman diet or the primal diet, the paleo diet allows for healthy, whole foods such as free-range, grass-fed meat, wild-caught fish, eggs, vegetables, nuts and seeds. In general, anything that could be found or hunted over 10,000 years ago is included in the paleo diet.
Fruits are consumed only in limited amounts in their whole food form. For example, if cavemen wouldn’t have blended 20 oranges into a 16-ounce juice, you won’t be able to either. For the same reason, “natural” sweeteners are avoided due to the high concentration of sugar that would never be found in nature.
Grains, legumes and dairy products are avoided for their high carbohydrate content and their damaging effect on the body’s intestinal lining. Some people on the paleo diet consume grass-fed butter and fermented dairy products in limited amounts, although the purists would say these are off-limits.
The Paleo Diet and Intermittent Fasting
Both the paleo diet and intermittent fasting harken to an era where humans lived as hunters and gatherers, eating as food was available versus three steady meals per day.
Intermittent fasting and the paleo diet work together in the following ways:
- While fasting promotes insulin sensitivity and low blood sugar, the paleo diet prevents these numbers from spiking once you eat again.
- Grains cause a predictable inflammatory response in many people, by avoiding them, you reap the benefits of reduced inflammation achieved by fasting.
- A paleo diet prevents hunger and cravings by putting an end to the insulin spike and subsequent crash triggered by high glycemic foods. This makes it easier to stick with your fast.
- The paleo diet can help ensure your nutritional needs are met during intermittent fasting by focusing on protein intake and a variety of nutrient-rich vegetables instead of grains.
The IF Mimicking Diet
How does the fasting mimicking diet work? The intermittent fasting mimicking diet, or FMD, differs from intermittent fasting in that you continue to eat, albeit very small amounts, during the “fasting” window. Usually, a fasting mimicking diet lasts for about five days, during which you consume 40% of the calories you normally would.
Proponents of the IF mimicking diet say that it offers similar benefits to intermittent fasting, while putting less stress on the body and mind, and is especially helpful for those new to fasting who may find it stressful to completely abstain from food for 12 hours or more.
Different from long-term calorie restriction, the FMD is considered safe because calories are restricted for no more than five days. It’s recommended to repeat this five-day diet twice yearly, quarterly or as often as once per month.
IF Mimicking Diet How-Tos
Fasting mimicking diets are vegetarian and free from gluten or lactose. A typical day may include tea and a small nut bar for breakfast, vegetable or miso soup for lunch, a handful of olives as an afternoon snack and another small bowl of soup for dinner.
Calories are restricted to anywhere from 700-1,200 per day. Five-day protocols gradually taper calories from 1,200 on Day 1 to 700 on Day 5. 35-55% of the caloric intake comes from carbohydrates, another 35-45% from fat, with the remaining 9-10% from protein.
IF Mimicking vs Intermittent Fasting
It’s possible to combine IF mimicking with intermittent fasting for a five-day window in one of two ways. Those on a 16:8 fast would consume the day’s small snacks and meals within an eight-hour window. Alternatively, you could slowly reduce calories from 1,200 to 700 over four days, then close the FMD with a 24-hour fast.
While an intermittent fasting protocol is potentially ongoing, it’s important to remember that the FMD is not a long-term diet. After five days or more of caloric restriction, results diminish as the body goes into starvation mode, slowing metabolism, holding on to fat and keeping glucose in your blood. While some find the FMD a good introduction to intermittent fasting, it should not be done in conjunction with intermittent fasting over a long period of time.
Whole Foods Are Really All You Need
Among the benefits of intermittent fasting is that, during the eating window, you consume your full caloric requirement via healthy meals. The body continues to have its complete nutritional needs met while reaping the benefits of a periodic fast. Fasting for longer is not necessarily better. If it was, would we even need to eat at all?
When participating in an intermittent fasting cycle, you do need to eat during the eating window. How you choose to eat influences your health as it always does. While a specialty diet such as paleo, keto or FMD potentially boosts the effects of your fast, all it really takes are simple, healthy, whole-food meals to benefit from intermittent fasting.