How to get started with intermittent fasting
Let’s say you want to give intermittent fasting a shot. How should you get started?
It comes down to shortening the number of hours you eat in a day.
Gutschow recommends starting with small fasts to see how your body reacts. On your first day, try skipping breakfast in the morning and see how you feel.
From there, you can build up to longer fasts. Maybe the following day, you also stop eating after the last meal of the day—for example, at 7 p.m. That means no post-dinner or late night snacks.
After taking small steps into intermittent fasting, you can try working your way up to a plan like 5:2 or 16/8 if it feels right for you.
What should you eat while intermittent fasting?
Because intermittent fasting targets when you eat, you might wonder if you can eat whatever you want on an intermittent fasting plan.
It’s true that some people eat lots of sweet and processed foods while on intermittent fasting. However, experts say feeding your body nutritious foods is essential.
Gutschow recommends trying to strike a balance between nutrient-dense options (think whole grains, vegetables, and lean proteins) and the treats you crave.
Opting for healthy foods during your non-fasting window can help you keep your calorie intake in check while giving your body what it needs to function at its best.
If you need more guidance, our intermittent fasting guide can help.
FAQs: Side effects of intermittent fasting
Some question the safety of intermittent fasting while others swear by it, so it’s natural to wonder if it’s a safe and effective approach.
To help us learn more, Gutschow shares answers to common questions about the side effects of intermittent fasting.
Does intermittent fasting cause muscle loss?
Intermittent fasting research is limited—current studies tend to focus on weight loss, so we don’t have a clear picture of how intermittent fasting may affect muscle mass (yet).
Here’s what we do know: When you reduce your calorie intake, it’s possible for you to lose muscle mass in addition to fat. But by introducing muscle-building exercises (like strength training) and consuming lean protein, you can lower your chances of losing muscle.
That may explain the results of one study, which suggests that intermittent fasting doesn’t have much effect on your ability to maintain muscle mass when combined with resistance training.
If keeping or increasing muscle mass is important to your weight loss journey, it’s a good idea to chat with your healthcare provider for guidance.
Does intermittent fasting cause mood swings or irritability?
If you’ve ever forgotten to pack a lunch, you’re familiar with the mood swings that can come from feeling extra hungry.
Gutschow says that for some, intermittent fasting can cause similar feelings of irritability—but if this happens, these feelings are usually short-lived and resolved within a few weeks.
Moodiness and irritability can be caused by sudden drops in blood sugar, so it’s important to make sure you’re getting enough calories during your eating window.
On the bright side, one small study also found that participants on intermittent fasting plans experienced positive feelings, like a sense of pride and achievement.
Will intermittent fasting give me headaches?
According to Gutschow, headaches are possible in the first few weeks of an intermittent fasting plan.
But research shows most headaches occur after 16 hours of fasting and get better after eating. Limiting your fasting window to 16 hours or less can help reduce your chances of headaches.
Make sure you’re also eating enough and staying hydrated.
Does intermittent fasting slow down your metabolism?
The short answer? Maybe.
Studies seem to differ when it comes to metabolism and intermittent fasting.
Some indicate that long-term intermittent fasting may slow your metabolism, while others conclude that short-term fasting can potentially give it a boost.
Why is this?
Short-term fasting may increase the stress hormone norepinephrine. When elevated, norepinephrine causes a spike in blood sugar, giving your body extra energy. These events temporarily raise your body’s resting energy needs and boost your metabolism.
On the other hand, Gutschow says restricting food for an extended period (24 hours or longer) may do the opposite. Long fasts can cause your body to adapt to having fewer calories.
The result? Your body slows metabolism and holds onto excess calories for energy.
Remember, this adaptation happens as a result of long-term calorie restrictions—which means it can happen with any restricted eating plan, not just intermittent fasting.
Does intermittent fasting cause diarrhea or constipation?
While it’s not a sure thing, Gutschow explains that fasting may cause temporary digestive upsets.
Your gut microbiome is ultra-sensitive to changes in eating patterns and food, so any big changes to your habits can mess with your bowel habits, especially early on.
Intermittent fasting can positively affect gut bacteria, but even good changes can make things feel a little out of balance at first.
The good news is, you can take steps to make the transition easier. Gutschow suggests drinking plenty of water and eating plenty of fresh fruits and vegetables to aid in digestion.
Be patient, and any temporary discomfort should pass. Also, be sure to choose foods carefully when breaking your fast. Gutschow notes that it can also be helpful to limit foods that commonly lead to digestive upset, like overly fatty, fried, or processed foods.
How Noom can work with intermittent fasting
If you’re trying intermittent fasting, it can be helpful to get support.
Noom Weight has a personalized curriculum (along with food logging, guides, and coaching) that can support you on your journey. Noom’s color system and focus on calorie density can also help guide food choices during the times you’re not fasting.
Learn more about how Noom can work with intermittent fasting.
