Sydney Bueckert
Fitness Trainer
CES, FNS, GPTS, NASM-CPT
Headlines make intermittent fasting seem like a miracle diet. And at a glance, it kind of is. A plethora of studies suggest that this style of fasting may help you lose weight, boost metabolic health, and maybe even live longer (1, 2, 3).
While the health-boosting effects of intermittent fasting may be true, context also matters. For example, while IF is all about when you eat, what you eat, it is important to be careful with what you are eating when you break the fast each day. And for mid- to older-aged adults, skipping out on nutrition can exacerbate muscle loss—which is also key for longevity.
Wondering if intermittent fasting is right for you? Here’s what you should know before deciding.
What Is Intermittent Fasting?
Intermittent fasting focuses on when you eat rather than what you eat. It works by dividing your day or week into structured periods of eating and fasting.
While the idea of fasting may sound extreme, it often starts with a simple extension of the time you already go without food. Many people naturally stop eating in the evening and don’t eat again until the next morning. Intermittent fasting builds on that gap by intentionally lengthening it.
Most intermittent fasting approaches follow a daily schedule. One of the most popular is the 16:8 method, which involves fasting for 16 hours each day and eating all meals within an 8-hour window.
Benefits of Intermittent Fasting
A growing body of research suggests intermittent fasting might help with weight loss, metabolic health, heart health, and brain function by reducing inflammation, improving insulin sensitivity, and lowering blood pressure. Here’s the scoop.
Lose weight
Studies suggest intermittent fasting is about as effective for weight loss as traditional calorie restriction (1). By limiting your daily eating window, you naturally eat fewer calories.
Intermittent fasting proponents argue that the potential metabolic benefits like better blood sugar control, reduced inflammation, and greater metabolic flexibility—might make it even easier to keep weight off long-term. While true, it’s worth noting that traditional calorie restriction comes with these perks, too.
Improve metabolic health
Intermittent fasting has been shown to reduce insulin resistance and fasting insulin levels (2), which supports metabolic health and reduces your risk of type 2 diabetes.
Fasting for over 12 hours can also trigger what’s known as the “metabolic switch,” where your body shifts from primarily burning glucose to fat for energy (4). Researchers believe there may be benefits to cyclic metabolic switching (which occurs during many Intermittent Fasting protocols) influencing mitochondrial, hormone, and even gut health, but more research is needed (5).
Boost heart health
Studies on intermittent fasting and heart health are mixed. Many suggest benefits like improved blood pressure, cholesterol, and weight loss, which are linked to better heart health (6).
However, a large (but not yet peer-reviewed) 2024 study associated 8-hour eating windows with earlier cardiovascular death (7). The study authors note that more long- term research is needed, highlighting that the risk may be higher for those with existing heart conditions, and that structured fasting may differ from unintentional meal skipping.
Other research points to Intermittent Fasting being no more effective than calorie restriction for cardiometabolic benefits (8). So, it may be worth talking to your doctor about the safest and most effective method for improving heart health for you.
Improve brain health
Eating less often may have benefits for your brain. A small 2024 randomized controlled trial suggests that intermittent fasting may improve executive function and memory, as well as reduce brain aging in older adults (9).
Scientists are still discovering exactly how fasting benefits the brain. One leading theory is that fasting triggers autophagy, a process where cells recycle old, damaged parts and waste to produce the building materials and energy for regenerating cells (10). In other words, It may help keep your neurons (brain cells) and other cells healthy.
Simplify dieting
If you struggle to stick to a traditional diet like calorie restriction, intermittent fasting is about as simple as it gets. Rather than calculating calories and planning meals, you can just focus on when (and when not to) eat.
Pros and Cons of Intermittent Fasting
Intermittent fasting may help improve several health markers, but it’s not for everyone. If you’re thinking of trying a fast, consider these pros and cons.
Pros
Fasting is straightforward. You don’t have to track meals or count calories, and it’s simple to fit into your day. Plus, studies show fasting can be good for you. Key benefits may include:
- Weight loss
- Lower cholesterol
- Lower blood pressure
- Lower blood sugar
- Reduced insulin resistance and improved insulin sensitivity
- Reduced inflammation
- Better brain health
- Cellular repair and maintenance
- Fewer age-related diseases
- Longer life
Cons
Fasting is simple, but that doesn’t mean it’s always easy. Here are some of the downsides to look out for.
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Initial side effects: Look out for hunger, headaches, fatigue, and irritability.
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Risk of overeating: IF doesn’t restrict food choices, so eating too much or making unhealthy choices might negate any benefits.
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Nutrient deficiencies: Getting enough of certain nutrients, like vitamins and minerals, fiber, and protein, can be difficult with shorter eating windows.
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Hormonal issues: Extended fasting can stress the body, which may impact hormone health, especially in women (11).
Should You Try Intermittent Fasting?
Intermittent fasting may have big benefits for certain people, but it’s not for everyone. Fasting might not be a good idea for certain groups or people with some health problems. Skip fasting (or talk to a doctor first) if you:
- Are over 65
- Are still growing (kids, teens, and young adults)
- Have diabetes
- Have heart, kidney, or liver disease
- Have a history of disordered eating
- Are pregnant or breastfeeding
- Have low blood pressure
- Take medications such as blood thinners, diuretics, blood pressure medications, or medications that affect your blood sugar
If you don’t have the above health concerns, and intermittent fasting makes you feel good and fits into your everyday lifestyle, it may be a simple way to achieve your health goals. But before making any drastic changes to your diet it is important to always check with your personal health provider.
If you try intermittent fasting and don’t like it, or aren’t seeing progress towards certain health markers, it’s perfectly okay to pivot. Nutrition is individual, and what works for some may not work for others. The good news is that research points to traditional calorie restriction and making healthier food choices as having many of the same health benefits as fasting.
How To Intermittent Fast
There are several intermittent fasting protocols, all of which split your days or weeks into periods of eating and fasting. Here are a few of the most popular ways to do it:
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The 16:8 Method: Restrict all eating to an 8-hour time block—12:00PM - 8:00PM, for example—then fast for the remaining 16 hours.
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The Eat-Stop-Eat Method: Fast for 24 hours a few days of the week, then eat on a regular schedule the rest of the week.
- The 5:2 Method: Eat only 500 calories a day 2 non-consecutive days out of the week and eat normally the rest of the week.
Regardless of the method, your mission is simple: Eat all your food within the eating window, and don’t eat when fasting.
Intermittent Fasting Tips
If you’re thinking about starting an intermittent fasting regimen, keep these tips top-of-mind.
Get goal-specific
Think about your goals for fasting: weight loss, metabolic health, a longer life? And consider your other goals: build muscle, run a marathon, just get healthy? Choose the approach that best supports the nutrition necessary for your desired outcome.
Consider your lifestyle
If family dinners are important to you, eating dinner solo at 4 p.m. isn’t going to work. Tweak your schedule to fit your life.
Eat well
Intermittent fasting isn’t a substitute for healthy eating. Aim to fill your plates with plenty of protein, healthy fats, whole grains, fruits, and veggies to fuel your everyday life.
Stay hydrated
Make sure to drink plenty of water while you’re fasting so you don’t get dehydrated. Water, sparkling water, no-sugar-added electrolytes, coffee, and tea are all good no- to low- calorie options that keep you hydrated without breaking a fast.
Ease in
The biggest health benefits from any diet come when you can stick to it long term. Don’t be afraid to start with bigger eating windows and smaller fasting window and adjust as you gain more confidence.
Plan workouts accordingly
Planning your workout schedule with enough time to fuel before and after your workouts will ensure you have the energy to put your best foot forward and properly recover. Track your workouts with the SunnyFit app: Low-intensity yoga or stretching is an excellent choice during your fasting window. Download the app now for free classes.
The Bottom Line
Recent research suggests intermittent fasting may help you lose weight, improve metabolic health, boost heart health, and brain health. Plus, many people find it easier to stick to than traditional dieting with similar effects. Still, Intermittent Fasting is not perfect for everyone so, consider the facts and talk to your doctor to see if intermittent fasting is right for you.
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