Intermittent fasting has become an increasingly popular way to lose weight and improve health. It involves cycling between periods of fasting and eating. Many people find it is an effective way to lose weight without counting calories or restricting foods. However, some wonder whether you can eat junk food during the eating periods and still experience the benefits.
What is Intermittent Fasting?
Intermittent fasting (IF) is an eating pattern that involves regular fasting periods. There are several different intermittent fasting methods, including:
- The 16/8 method: Fast for 16 hours per day and restrict eating to an 8-hour window.
- The 5:2 diet: Fast or restrict calories to 500–600 per day for 2 days per week and eat normally the other 5 days.
- Alternate day fasting: Fast every other day.
- The warrior diet: Eat small amounts of raw fruits and vegetables during the day and one large meal at night.
- Periodic fasting: Fast for 24-hour periods 1–2 times per week.
The most common approach is the 16/8 method, where you fast for 16 hours per day and eat during the remaining 8-hour window. For example, you might skip breakfast and only eat between 12–8 pm daily.
Benefits of Intermittent Fasting
Here are some of the evidence-based benefits of intermittent fasting:
- Weight loss: Many studies show intermittent fasting leads to greater weight loss and fat loss compared to traditional calorie restriction (1, 2, 3).
- Heart health: Intermittent fasting may reduce heart disease risk factors like LDL cholesterol, blood pressure, inflammation, and blood sugar levels (4, 5).
- Brain health: IF may boost brain function and prevent neurodegenerative disorders. It increases growth factors that are important for brain health (6, 7).
- Cell repair: Restricting calories and fasting intermittently may help cells repair and renew themselves more efficiently (8).
- Longevity: Some research indicates intermittent fasting may extend lifespan by slowing aging and disease processes (9).
Keep in mind that more research is still needed on intermittent fasting itself, including its long-term effects and ideal schedule. However, the evidence is clear that it can be an effective way to lose weight and improve health.
Can You Eat Junk Food While Intermittent Fasting?
This is the million dollar question. Since intermittent fasting does not restrict specific foods or food groups, it seems you should be able to eat whatever you want during the eating periods.
In theory, you could eat only junk food every day within your 8-hour window and lose weight, as long as you maintain a calorie deficit. A calorie deficit is when you consume fewer calories than you burn.
However, just because you can technically eat junk food and lose weight does not mean it is optimal for health.
Potential Problems with Eating Junk Food While Intermittent Fasting
Here are some potential downsides to eating mostly junk food within your eating window:
- Lack of nutrients: Junk food is often highly processed and lacking in vitamins, minerals, fiber, and other nutrients your body needs.
- Hunger and cravings: Junk food is often not very satiating. You may get hungry sooner and crave more sugar and refined carbs.
- Energy crashes: Processed junk foods can cause spikes and crashes in blood sugar levels, resulting in low energy.
- Gut health: A diet full of processed foods can negatively impact gut bacteria linked to immunity, mood, and health.
- Disease risk: Those who eat more processed meats and junk food have a higher risk of diseases like heart disease, diabetes, and cancer.
- Accelerated aging: Diets high in sugar and refined carbs may accelerate aging processes like skin aging and cognitive decline.
While intermittent fasting itself offers many benefits, pairing it with a poor diet high in junk food will likely minimize those benefits.
Healthier Food Choices While Intermittent Fasting
To maximize the health benefits of intermittent fasting, focus on nutritious whole foods during your eating window. Here are some healthy food choices:
Proteins
- Fatty fish like salmon
- Grass-fed beef
- Organic chicken
- Eggs
- Legumes
- Nuts and nut butters
Fruits and Vegetables
- All fresh fruits and vegetables
- Fresh green leafy vegetables
- Cruciferous veggies like broccoli and cauliflower
- Berries
Whole Grains
- Oats
- Quinoa
- Brown rice
- Barley
- Buckwheat
Healthy Fats
- Olive oil
- Coconut oil
- Ghee
- Avocados and avocado oil
- Nuts and seeds
Filling your diet with these nourishing foods will help ensure you get a wide range of vitamins, minerals, fiber, and antioxidants. This will maximize health and prevent nutrient deficiencies.
Can You Have Any Junk Food While Intermittent Fasting?
It’s understandable that most people don’t want to completely eliminate junk foods and sweets when intermittent fasting. The key is finding balance and limiting junk food intake.
Here are some general guidelines on how to healthfully incorporate some junk foods:
- 80/20 rule: Aim for 80% of your diet to come from healthy whole foods. Leave 20% for treats and junk foods you enjoy.
- Focus your junk food intake in the beginning of your eating window when you’re less likely to overeat it.
- Savor small amounts of junk foods slowly. Don’t mindlessly overconsume them.
- Be picky about your junk food choices. Pick your favorite treats and ones with some redeeming qualities like dark chocolate.
- Always pair junk foods with protein, fat, fiber, or greens. Never eat them alone on an empty stomach.
Here are some examples of pairings that help minimize junk food downsides:
- French fries with garlic aioli (adds protein from eggs in mayo)
- Pizza with a big green salad (adds fiber and nutrients)
- A burger wrapped in lettuce (adds fiber and nutrients)
- Ice cream with fresh berries (adds fiber and antioxidants)
Healthier Alternatives to Common Junk Foods
You can also try substituting healthier alternatives of popular junk foods and treats. Here are some ideas:
| Junk Food | Healthy Alternative |
|---|---|
| Potato chips | Kale chips, beet chips, parsnip chips |
| French fries | Baked sweet potato fries |
| Candy bars | Trail mix with nuts, seeds, and dark chocolate chips |
| Pizza | Cauliflower crust pizza with veggies |
| Ice cream | Frozen banana “ice cream” |
| Cookies | Energy balls with nuts, oats, and dried fruit |
| Sugary sodas | Sparkling water with fruit juice |
Swapping out heavily processed junk foods for healthier alternatives can help satisfy cravings while providing more nutrients.
Sample Menus with Some Junk Food
To give you an idea of how to healthfully mix junk food with whole foods, here are some sample menus:
16/8 Schedule with 12–8pm Eating Window
Meal 1:
- Scrambled eggs with spinach and avocado
- Berries
Meal 2:
- Grilled chicken sandwich on whole grain bread with lettuce, tomato, and mustard
- Side salad with vinaigrette
Meal 3:
- burger wrapped in lettuce with oven-baked fries
- Dark chocolate square (1 oz)
5:2 Schedule with 500 Calories on Fasting Days
Meal 1:
- Scrambled egg white with vegetables (100 calories)
- 1 slice whole wheat toast with peanut butter (150 calories)
Meal 2:
- Tuna salad with light mayo on greens (150 calories)
- 1 small apple with 1 Tbsp. almond butter (100 calories)
Meal 3:
- Vegetable soup (100 calories)
- 1 oz. dark chocolate (100 calories)
On fasting days, focus on lean proteins, fruits, vegetables and healthy fats. Limit added sugars and refined carbs.
The Bottom Line
While intermittent fasting does not strictly prohibit junk foods, filling your diet with processed snacks high in sugar and refined carbs can minimize its benefits.
It’s best to focus on whole, minimally processed foods for 80-90% of your meals and reserve a small portion of your calories for your favorite treats. Pair junk foods with proteins, fats or veggies to help control hunger and cravings.
Additionally, try substituting healthier alternatives that satisfy your cravings for junk food when possible. This will provide more nutrients and potentially better results over the long-term.
