Of all the fad diets of the moment, intermittent fasting has garnered much attention for its convincing evidence in scientific literature. Throughout history, fasting has been utilized as an expression of political dissent, desire for spiritual reward, as well as a therapeutic tool, but only recently has it gained widespread traction among fitness gurus for its touted weight loss and anti-aging effects. But that brings the big question: is there an ultimate intermittent fasting guide so you know what to eat while you’re on this diet?
First, let’s take a step back and break down the basics: How does the diet work when it comes to these major intermittent fasting health benefits? Scientists postulate that the anti-aging benefits are largely due to increased insulin sensitivity, and weight loss is related to an overall reduced calorie intake because of a shortened feeding window. Simply put, when you have less time during the day to eat, you eat less. Easy, right? But a key concept, as with any diet, is determining feasibility for your lifestyle.
One recent The Lancet Diabetes & Endocrinology study showed diet-induced weight loss typically leads to a 70 percent regain in weight, so finding any type of weight-loss plan that works best for you and won’t cause you any damage in the future is the key.
There are many different methods one could follow with intermittent fasting, but Andres Ayesta, MS, RDN, registered dietitian and expert in the field of fasting, says that the time restricted feeding (TRF) approach is the best option for working adults.
“Fasting from 9 p.m. until about 1 p.m. the next day works well because most people are already skipping breakfast or are eating poor ones,” Ayesta says. This approach can work well around a day job, but Ayesta also emphasizes the importance of maintaining dietary needs around this time restricted feeding window. This means that overall diet quality and habitual food choices still matter while intermittent fasting and that you probably won’t get the body of your dreams while chowing down on nothing but hamburgers and fries. In fact, eating junk food in a condensed feeding window on the IF diet may actually put you at risk of a shortfall of key nutrients such as calcium, iron, protein, and fiber, all of which are essential for normal biological function. Plus, consuming a diet rich in fruits and vegetables allows for more antioxidants in your body, which, like the metabolic effects of intermittent fasting, may contribute to a longer lifespan!
For starters, here’s a breakdown of typical intermittent fasting schedules:
- Alternate Day Fasting (ADF)—1 day ad libitum eating (normal eating) alternated with 1 day complete fasting
- Modified Alternate Day Fasting (mADF)—1 day ad libitum feeding alternated with 1 day very low-calorie diet (about 25 percent of normal caloric intake)
- 2/5—Complete fasting on 2 days of the week with 5 days ad libitum eating
- 1/6—Complete fasting on 1 day of the week with 6 days ad libitum eating
- Time Restricting Feeding (TRF)—Fasting for 12-20 hours per day (as a prolongation of the nighttime fast) on each day of the week. “Feeding window” of 4-12 hours
OK, so you have the time windows for when you can chow down, but you’re probably wondering what to eat during your IF journey. We rounded up 20 of the best foods to create the ultimate intermittent fasting food guide that will help prevent nutrient shortfalls!
One of the most important aspects of maintaining a healthy eating pattern while intermittent fasting is to promote hydration. As we go without fuel for 12-16 hours, our body’s preferred energy source is the sugar stored in the liver, also known as glycogen. As this energy is burned, so disappears a large volume of fluid and electrolytes. Drinking 8+ cups of water per day will prevent dehydration and also promote better blood flow, cognition, and muscle and joint support during your intermittent fasting regimen.
What about a warm cup of Joe? Will a daily Starbucks run break the fast? It’s a common question among newbie intermittent fasters, but worry not: coffee is allowed. Because in its natural state coffee is a calorie-free beverage, it can even technically be consumed outside a designated feeding window, but the minute syrups, creamers, or candied flavorings are added, it can no longer be consumed during the time of the fast, so that’s something to keep in mind if you usually doctor up your drink.
Carbohydrates are an essential part of life and are most definitely not the enemy when it comes to weight loss. Because a large chunk of your day will be spent fasting during this diet, it is important to think strategically about ways to get adequate calories while not feeling overly full. Though a healthy diet minimizes processed foods, there can be a time and place for items like whole grain breads, bagels, and crackers, as these foods are more quickly digested for fast and easy fuel. If you intend to exercise or train regularly while intermittent fasting, these will especially be a great source of energy on the go.
Fiber—the stuff that keeps you regular—was named a shortfall nutrient by the 2015-2020 Dietary Guidelines, and a recent article in Nutrients stated that less than 10 percent of Western populations consume adequate levels of whole fruits. With 8 grams of fiber per cup, raspberries are a delicious high fiber fruit to keep you regular during your shortened feeding window.
This nutritious superstar packs a high fiber punch with 32 percent of total daily fiber needs met in only half a cup. Additionally, lentils provide a good source of iron (about 15 percent of your daily needs), another nutrient of concern, especially for active females undergoing intermittent fasting.
Similar to breads, white potatoes are digested with minimal effort from the body, and if paired with a protein source, they are a perfect post-workout snack to refuel hungry muscles. Another benefit making potatoes an important staple for the IF diet is that once cooled, potatoes form a resistant starch primed to fuel good bacteria in your gut.
The EAT-Lancet Commission recently released a report calling for a dramatic reduction in animal-based proteins for optimal health and longevity. One large study directly linked consumption of red meat to increased mortality. Make the most of your anti-aging fast by incorporating life-extending plant-based protein substitutes like seitan. Also known as “wheat meat,” this food can be battered, baked, and dipped in your favorite sauces.
One of the creamiest and tastiest dips known to mankind, hummus is another excellent plant-based protein and is a great way to boost nutritional content of staples like sandwiches (just sub for mayonnaise!) If you’re adventurous enough to make your own, don’t forget the secret to the perfect recipe is ample garlic and tahini.
If your goal is to be a member of the centenarian club, you might want to read up on the Blue Zones. These five geographical regions in Europe, Latin America, Asia, and the U.S. are well known for dietary and lifestyle choices linked to extreme longevity. One commonly consumed food across these zones is salmon, which is high in brain-boosting omega-3 fatty acids EPA and DHA.
As if we needed another excuse to splurge for an appetizer at the sushi bar, isoflavones, one of the active compounds in soybeans, have demonstrated to inhibit UVB induced cell damage and promote anti-aging. So, next time you host a dinner party in, impress your guests with a delicious recipe featuring soybeans!
One of the proposed mechanisms behind why IF leads to weight loss is due to the fact that the individual simply has less time to eat and therefore eats less. While the principle of energy in versus energy out holds true, something that isn’t often discussed is the risk of vitamin deficiencies while in a caloric deficit. Though a multivitamin is not necessary with a balanced diet of plenty of fruits and vegetables, life can get hectic, and a supplement can help fill the gaps.
If a daily supplement doesn’t sound appealing, try springing for a double dose of vitamins by creating homemade smoothies packed with fruits and vegetables. Smoothies are a great way to consume multiple different foods, each uniquely packed with different essential nutrients.
Quick tip: Buying frozen can help save money and ensure ultimate freshness.
Vitamin D Fortified Milk
The recommended intake of calcium for an adult is 1,000 milligrams per day, or in plain speak, 3 cups of milk per day. With a reduced feeding window, opportunities to drink this much might be scarce, and so it is important to prioritize high calcium foods. Vitamin D fortified milk enhances the body’s absorption of calcium and will help to keep bones strong. To boost daily calcium intake, you can add milk to smoothies or cereal, or even just drink it with meals. If you’re not a fan of the beverage, non-dairy sources high in calcium include tofu and soy products, as well as leafy greens like kale.
A glass of wine and a night of beauty sleep may keep heads turning, as the polyphenol found in grapes has distinct anti-aging effects. Humans are known to have one of the enzyme classes SIRT-1, which is thought to act upon resveratrol in the presence of a caloric deficit to enhance both insulin sensitivity and longevity.
Don’t let their miniature size fool you: Blueberries are proof that good things come in small packages! Studies have shown that longevity and youthfulness is a result of anti-oxidative processes. Blueberries are a great source of antioxidants and wild blueberries are even one of the highest sources of antioxidants. Antioxidants help rid the body of free radicals and prevent widespread cellular damage.
During the final hours of your fast, you’ll likely start to feel the effects of hunger, especially as you first start intermittent fasting. This “hanger” may, in turn, cause you to overeat in large quantities, leaving you feeling bloated and lethargic minutes later. Papaya possesses a unique enzyme called papain that acts upon proteins to break them down. Including chunks of this tropical fruit in a protein-dense meal can help ease digestion, making any bloat more manageable.
Make room on the cheese board for a mixed assortment, because nuts of all varieties are known to rid body fat and lengthen your life. A prospective trial published in the British Journal of Nutrition even associated nut consumption with a reduced risk of cardiovascular disease, type 2 diabetes, and overall mortality.
Of course, you’ve heard a drizzle of olive oil has major health benefits, but there are plenty of other oil options out there you can use, too. You don’t want to heat an oil you’re cooking with beyond its smoke point, so next time you’re in the kitchen whipping up a stir-fry, consider using ghee as your oil of choice. Basically just clarified butter, it has a much higher smoke point—making it a great choice for hot dishes.
Homemade Salad Dressing
Just like your grandmother kept her cooking wholesome and simple, so should you when it comes to salad dressings and sauces. When we opt to make our own simple dressings, unwanted additives and extra sugar are avoided. In fact, according to this article Dihub in a dermatological journal, sugar might be accelerating the aging process more than any other ingredient by degrading cross-linkages of collagen fibers in our skin.
Branch Chain Amino Acid Supplement
A final IF-approved supplement is the BCAA. While this muscle-building aid is most beneficial for the individual who enjoys fasted cardio or hard workouts at the crack of dawn, it can be consumed all throughout the day (fasting or not) to prevent the body from going into a catabolic state and preserve lean muscle mass. Note: If you choose to follow a vegan diet pattern, this supplement may be off limits, as most are sourced from duck feathers.