Fasting isn’t new. In fact, it predates Instagram influencers, juice cleanses, and even the invention of sliced bread. If you flip back to 2nd Samuel in the Bible (circa 1010 B.C.), you’ll find references to fasting. That’s about a thousand years before the first Kardashian krawled out of the primordial goo and posted a filtered selfie on "The Daily Papyrus."
But lately, intermittent fasting has become the trendiest thing since cold plunges and functional mushrooms. Some say it’s a fat loss miracle. Others warn it’s just starvation with a rebrand. So what’s the truth? Can intermittent fasting actually help you lose fat, feel better, and stop obsessing over your next snack?
Let’s dig in.
What Is Intermittent Fasting?
Intermittent fasting (IF) is not a diet—it’s a schedule. It’s about when you eat, not necessarily what you eat. You cycle between periods of eating and periods of not eating, ranging from a few hours to a full day.
There are several popular approaches, but the 16:8 method (16 hours fasting, 8 hours eating) and 24-hour fasts once per week are two of the most widely used.
And no, skipping breakfast once doesn’t mean you’ve gone “full monk mode.”
How Does Intermittent Fasting Help With Weight Loss?
Let’s get one thing straight: you lose weight when you consume fewer calories than you burn. That’s true of keto, veganism, Mediterranean, or the infamous cotton ball diet. IF just makes that process easier for a lot of people. Here’s why:
Caloric Restriction Without Micromanagement
When your eating window is shortened, you're naturally eating fewer meals. Fewer meals = fewer opportunities to snack on whatever's lurking in your pantry. Many people find they lose fat without needing to count calories obsessively.
Hormonal Reset: Insulin, Leptin, and Ghrelin
Most people walk around with chronically high insulin due to constant eating. High insulin levels block fat burning and mess with hunger cues. Fasting gives your body a chance to bring insulin down and re-sensitize your cells.
It also helps balance ghrelin (the “I’m starving” hormone) and leptin (the “I’m full” hormone). Constant snacking wrecks these. Fasting can bring them back online.
Autophagy: Your Built-In Repair System
Fasting activates autophagy, a natural process where your body recycles damaged cells and clears out junk. It’s like cellular spring cleaning. This can lead to better energy, improved immunity, and even anti-aging effects.
Shrinks Your Appetite (Literally)
Going 16–24 hours without food can help shrink your stomach slightly. That burrito that used to disappear in 4 bites? Now it might actually fill you up. Fasting resets your hunger baseline, helping you eat less even when you're not fasting.
Is Intermittent Fasting Safe for Women?
This is where things get nuanced.
Men tend to thrive on 16:8 fasting. Long fasts often enhance mental focus, energy, and fat burning by activating the sympathetic nervous system. Historically, this would have helped with things like chasing mammoths and hunting elk.
Women, however, have a more complex hormonal landscape. The female body is designed to protect reproductive health. Fasting too often or too long can send the signal that resources are scarce, which may disrupt cycles, reduce energy, and increase stress hormones.
The takeaway: women can fast, but the frequency and style need to be different. Most women do better with occasional 20–24 hour fasts, not daily fasting windows.
Best Intermittent Fasting Methods (By Goal)
16:8 Fasting (Best for Men)
Fast for 16 hours, eat during an 8-hour window. Skip breakfast, eat your first meal around noon, and stop eating by 8 p.m. This is great for maintaining leanness, increasing focus, and simplifying your day.
Ideal for men and postmenopausal women.
24-Hour Fasting (Best for Most Women)
Once per week, eat an early dinner (6 or 7 p.m.), then fast until the same time the next evening. Drink water, black coffee, or tea throughout the day.
This method supports hormonal balance, autophagy, calorie reduction, and mental clarity—without over-stressing the body.
Warrior Diet (Advanced, Use With Caution)
20 hours fasting, 4 hours eating. This protocol may work for short bursts of fat loss, but it’s tough to sustain and can lead to nutrient deficiencies if not done carefully.
What to Eat (and Not Eat) When Fasting
What Breaks a Fast?
Anything that spikes insulin or blood sugar will break your fast. That includes:
- Carbs (even fruit)
- Protein shakes
- Fats (yes, even Bulletproof coffee)
- Any snack with calories
Water, electrolytes, FastAid, black coffee, and plain tea are fair game.
How to Break Your Fast Properly
Start with something nutrient-dense and easy to digest. A superfood shake, bone broth, or a salad with lean protein is ideal. Then have a balanced, whole-food meal with protein, healthy fats, and veggies.
Don’t break a fast with a basket of fries and a margarita unless you want to feel like trash.
What Supplements Can You Take During Intermittent Fasting?
One of the most common questions people ask is: “What supplements are OK to take while fasting?”
The answer depends on your goal—fat loss, autophagy, or maintaining energy—but there are several fasting-approved options that can enhance your results without breaking your fast.
Best Supplements to Take While Fasting
Electrolytes
Fasting causes your insulin levels to drop, which means your body flushes out sodium and water faster than normal. This can lead to dehydration, brain fog, and headaches—aka “the fasting flu.” To combat this, supplement with a clean electrolyte blend that includes sodium, potassium, and magnesium. Just make sure it contains no added sugar or carbs.
FastAid (Fasting-Safe Aminos)
This supplement was designed specifically for fasting. FastAid provides targeted amino acids that don’t spike insulin or blood sugar but can reduce hunger pangs and preserve muscle mass—especially useful before a workout or during longer fasts. It’s a great option if you're training fasted or need a little help pushing through a tough stretch without food.
Magnesium Glycinate
Magnesium is essential for over 300 biochemical processes in the body—including muscle recovery, sleep, and energy metabolism. Many people are deficient, especially while fasting. A supplement like magnesium glycinate won’t break your fast and can improve sleep and reduce cramps or irritability during prolonged fasts.
Vitamin D
Fat-soluble and crucial for immune health, hormone regulation, and energy. Vitamin D supplements are typically oil-based, but because they don’t spike insulin or blood glucose, they’re generally considered safe to take during a fast—especially if you’re not eating enough vitamin D-rich foods later in the day.
Deep Mind
This is a fasting-approved nootropic designed to enhance mental clarity, reduce brain fog, and keep you focused—without the blood sugar spike you’d get from sugary energy drinks or coffee creamer. Ideal during the second half of a longer fast when your brain needs a little boost.
Supplements to Avoid While Fasting
Protein Powders and Shakes
Even though they’re healthy, protein shakes stimulate insulin and break your fast. Save them for your eating window, ideally as part of your first post-fast meal.
Bone Broth
Often praised for its gut-healing properties, bone broth still contains protein and calories—meaning it breaks a fast. Use it to break your fast, not during it.
Typical Pre-Workout Supplements
Most pre-workouts include sweeteners, calories, or stimulants that trigger digestion and insulin. If you want a fasted-friendly pre-workout, go for FastAid or caffeine-only options like black coffee or Deep Mind.
How to Make Intermittent Fasting Work For You
- Eat enough protein: Aim for 0.9g per pound of bodyweight. Use protein supplements if necessary.
- Prioritize fat over carbs: Think eggs, avocado, nuts, coconut oil, and fatty fish.
- Sleep at least 7 hours: Fasting is a stressor. Recovery matters.
- Exercise smart: Short bodyweight circuits and low-intensity cardio work well on fasting days. Morning workouts are ideal.
- Listen to your body: If you feel depleted, overly hungry, or your sleep suffers—take a break from fasting.
Red Flags: When to Stop Fasting
Stop fasting or adjust your approach if you experience:
- Increased belly fat or water retention
- Missed menstrual cycles
- Persistent insomnia or low mood
You’re in this to improve your health—not tank your hormones.
Frequently Asked Questions
Can I drink BCAAs during a fast?
BCAAs spike insulin slightly, which may pause autophagy temporarily. They’re fine post-workout if you’re not eating for several more hours. They’re not required but can help with muscle retention and hunger.
Will fasting crash my metabolism or put me in starvation mode?
No. In fact, short-term fasting can improve insulin sensitivity and slightly increase growth hormone and metabolism. Chronic under-eating is more dangerous than strategic fasting.
Can I fast and still build muscle?
Yes, especially with a 16:8 window. Just make sure you’re eating enough protein and training hard. It’s harder with OMAD or extended fasts.
Does drinking Bulletproof coffee break my fast?
Yes. Any calorie-dense drink, even if it’s “just fat,” will start digestion and end autophagy. If fat loss is the goal, skip it.
When’s the best time to work out while fasting?
Late morning workouts (around 10–11 a.m.) are ideal. Break your fast shortly after with a high-protein meal. For 24-hour fasts, stick to light cardio or walking.
Should You Try Intermittent Fasting?
If you want fat loss, mental clarity, better blood sugar control, and fewer food decisions in a day—intermittent fasting can work.
Men: Try the 16:8 protocol first and see how you feel.
Women: Start with one 24-hour fast per week and monitor how your energy, sleep, and mood respond.
And remember: fasting isn’t about punishment or perfection. It’s a tool. Use it strategically—and always listen to your body.
Want to pair fasting with a nutrition plan that makes meals easy and results inevitable? Download my free Meal Planning Roadmap with 24 high-protein recipes you can prep in 15 minutes or less.