Intermittent Fasting: Meal Plan, Benefits & Flaws | Signos

Many people swear by intermittent fasting. But what foods can you actually eat on this diet plan? Find out this and more!

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by
Rebecca Washuta
— Signos
MS, CNS, LDN
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Reviewed by

Rebecca Washuta
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Updated by

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Science-based and reviewed

Published:
April 23, 2024
June 22, 2023
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Table of Contents

Intermittent Fasting has quickly become one of the most popular diets out there. Praised by influencers, doctors, and scientists alike, this eating pattern has been shown to help you lose weight, improve your mental clarity, and even increase your lifespan.1 While you should always consult a healthcare professional before starting a new dietary pattern, intermittent fasting can pose more risks than other diets, so it's important you practice it safely.

What is Intermittent Fasting?

So what exactly is intermittent fasting? Intermittent fasting (or IF) is a dietary pattern designed to incorporate brief periods of fasting into your routine. Unlike traditional fasting (often practiced for cultural or religious reasons), which can last days or weeks, intermittent fasting focuses on short-term fasts and offers more flexibility. 

With IF, you’re focused on when you eat instead of what you eat. Many people prefer this type of plan because it allows them to reap the benefits without restricting their favorite foods. With other diets, the ketogenic (keto) diet, for example, people are constrained to a very small number of foods. This lack of variety can make long-term adherence to the diet difficult. If you enjoy a wide variety of foods and don’t mind limiting when you eat, IF may be a good option for you. 

When your body is in a fasted state, and your glucose stores have been depleted, fatty acids become the main energy source for cells. Your body undergoes lipolysis, or the breakdown of stored fat, to provide the fuel you need. This can result in weight loss and reduced triglyceride and cholesterol levels.2 Fasting also stimulates autophagy, a housekeeping mechanism in which the body destroys damaged cells, proteins, and pathogens. This natural clean-up process can reduce inflammation, support cardiovascular health, and increase longevity.3 

Different types of IF offer various durations of the fasting period. This article will walk you through each form of IF, the pros and cons of this eating style, and provide detailed examples to get you started. Regardless of how hectic your schedule is, you’re bound to find an option that works for you. 

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Is It Better to Fast for 12 or 16 Hours?

Time-restricted fasting is the most common type of intermittent fasting. With this version of IF, you abstain from food for 12 (i.e., 12/12) to 16 (i.e., 16/8) hours daily. This means your eating window will be 8 to 12 hours. 

Both the 12/12 and 16/8 plans have significant benefits. The 12/12 option tends to be easier for people because it allows for more flexibility. The 16/8 version, however, has a more positive impact on weight loss and cellular repair.4 

What’s most important is staying consistent with your fasting and eating windows. If limiting your eating to an 8-hour window (as required with the 16/8 plan) seems like a stretch due to family, work, or social obligations, you will still see health improvements with the 12/12 version.

5 Health Benefits of Intermittent Fasting

IF has become widely popular for a good reason; it’s associated with many health benefits! This dietary pattern has been shown to:

Support weight loss

IF is an alternative way for people to lose comparable amounts of weight to traditional calorie-restricted diets. Reviews of 11 randomized trials of at least eight weeks following intermittent fasting in overweight or obese adults found equivalent weight loss in 9 of the 11 studies.6

IF focuses on when you eat, whereas regular diets focus on what you eat. There are no off-limit foods. For individuals who have struggled with food restrictions or are unwilling to eliminate certain foods, simply following fasting and eating windows can be an effective tool for weight loss.

Lower blood sugar2,7

Small studies ranging from 12 to 250 participants indicate intermittent fasting helps people lose weight and lower insulin levels, blood pressure, glucose levels after eating, triglyceride levels, cholesterol levels, and waist circumference.7

These improvements show that weight loss helps control blood sugar and metabolic risk. Further changes in diet to optimize nutrition consumed during the eating window can further improve chronic health conditions.

Increase insulin sensitivity

IF is also used to support blood sugar and insulin levels. Research suggests that IF helps people living with diabetes improve blood sugar levels without following the typical low-calorie weight loss advice.8

In human and animal studies, IF appears as effective (if not more) than caloric restriction to improve insulin sensitivity or how efficiently your cells can move sugar out of the blood.8,9 Further, IF can improve blood sugar and glycemic response without any other changes or dietary restrictions.10

The timing of the fast may also come into play, as one study found that an IF pattern where the first meal was earlier in the day improved beta-cell responsiveness (the cells in the pancreas that make insulin), insulin sensitivity, and markers of oxidative stress compared to a group eating later during a 12-hour window.11

Improve cognition and stimulate neurogenesis (growth of new neurons)

The power of autophagy extends to brain cells by removing aging and damaged cells, which could decrease the risk of neurological diseases.12 Inflammation is closely associated with the aging process. 

Fasting is also linked to improved cognitive function, including memory and neurodegeneration.13

Lower cholesterol and triglyceride levels

IF may also offer cardiovascular protection with or without weight loss by lowering cholesterol, blood pressure, and triglycerides.10,14 And as mentioned earlier, the inflammatory markers associated with increased risk of cardiovascular diseases are positively affected by intermittent fasting.2

Other Benefits:

Versatility

IF allows you to eat a wide range of foods and doesn’t require you to cut out any specific food groups. A diverse diet positively impacts your gut microbiome, reducing inflammation and supporting metabolic health.

Sustainability 

Most people yo-yo diet for years, trying different fad diets for a few weeks at a time. IF is flexible, allowing people to adhere to it long-term, which compounds the health benefits. 

Potential Drawbacks of Intermittent Fasting

While a large body of evidence supports IF, it’s not without its disadvantages.  If you’re considering starting IF, you should be aware of the potential drawbacks:

  • Fatigue and dizziness2
  • Irritability
  • Hypoglycemia
  • Hormone disruption2
  • Trigger eating disorders

What Can I Eat on an Intermittent Fasting Meal Plan?

The best part about IF is that all foods can be included. While focusing on a diet rich in high-quality protein and phytonutrients from plant foods is recommended and will improve your results, you’re not required to limit specific macronutrients or calorie intake. 

You can still enjoy your favorite foods during your chosen eating window. Most people following the 12/12 eating plan consume breakfast, lunch, and dinner and forgo late-night snacks. Those who follow the 16/8 diet plan typically eat two meals a day, skipping one meal (usually breakfast or dinner) to ensure they stay within the 8-hour eating period. 

The 12/12 Method

The 12/12 method is the most basic type of time-restricted IF. It requires you to eat within a 12-hour window (e.g., 7 am-7 pm) and then fast for 12 hours. This approach is highly adaptable, allowing you to eat breakfast, lunch, and dinner, as well as snacks, as long as you keep them within the 12 hours.

Example 12/12 Intermittent Fasting Plan and Schedule

7 am - Breakfast: Veggie Omelet with avocado toast 

10:30 am - Snack: Apple with almond butter

1:00 pm - Lunch: Caesar salad with salmon

3:30 pm - Homemade trail mix: Cashews, pumpkin seeds, dried cherries, dark chocolate chips

6:30 pm - Dinner: Roasted chicken with couscous and broccoli

The 16/8 Method

The 16/8 method is a more advanced type of time-restricted fasting where you fast for 16 hours daily, giving you only an 8-hour eating window. The longer fasting time increases the benefits, but it can be harder to implement as it usually requires skipping a meal. While you can choose the best eating window for your schedule, earlier windows (10 am-6 pm) vs. later windows (2 pm-10 pm) are associated with increased cardiovascular and metabolic benefits.4 

Example 16/8 Intermittent Fasting Schedule and Meal Plan

7:00 am - Breakfast: You will still be fasting at this time, so you can’t consume anything that will break your fast. The following beverages are permitted:

  • Water
  • Tea*
  • Black Coffee*

*You can add one tablespoon of heavy cream if desired, but no other milk or sweeteners

11:00 am - Lunch: Grilled shrimp salad with arugula, tomato, cucumber, and lemon olive oil dressing

3:30 pm - Snack: Greek Yogurt topped with berries and honey

7:30 pm - Dinner: Pasta with turkey meatballs, marinara, parmesan cheese, and a side of sauteed spinach

The Twice-a-Week (or 5/2) Method

This version of IF requires you to fast two days a week and allows you to eat as you normally would the remaining five days. This type of fast is for more experienced people, and you should talk to a healthcare professional before beginning.

The 5/2 plan offers flexibility in that you will be able to follow your normal routine most of the week. The two days you decide to fast, you will need to significantly cut your caloric intake, aiming for a maximum of 500 calories per day. You can spread your calories out or consume them during one meal. Focusing on hot beverages like teas and soups can make you feel fuller longer and help ward off hunger on your fasting days.

Example 5/2 Meal Plan and Schedule

7:00 am - Breakfast: You will still be fasting at this time, so you can’t consume anything that will break your fast. The following beverages are permitted:

  • Water
  • Tea*
  • Black Coffee*

*You can add one tablespoon of heavy cream if desired, but no other milk or sweeteners

12:00 pm - Lunch: 2 cups chicken bone broth and 15 almond flour crackers

3:30 pm - Snack: Herbal tea

7:00 pm - Dinner: 2 cups of veggie soup

7:30 pm - Dessert: 2 small pieces (20g) of dark chocolate

Alternate-Day Fasting Method

Alternate-day fasting (as the name implies) requires you to fast every other day for three to four fasting days each week. Similar to the 5/2 plan, you need to limit your intake to 500 calories or less on fasting days. This option offers the least amount of flexibility, making it the most difficult to implement. On the other hand, due to the increased fasting time with this method, you will likely see benefits much more quickly. You should consult with your healthcare provider to discuss potential risks and see if this level of intermittent fasting is right for you. 

Example Alternate-Day Schedule

Monday - Fast

Tuesday - Eat normally

Wednesday - Fast

Thursday - Eat normally

Friday - Fast

Saturday - Eat normally

Sunday - Fast

Best Practices for Beginners

So you’re interested in trying intermittent fasting but unsure where to begin? Try the tips below in this beginner’s guide to start things on the right foot.

  1. Time-restricted fasting is your best bet if you’re just starting with IF. Depending upon your normal eating schedule, you can determine which option, 12/12 or 16/8, feels right for you. 
  1. You can begin by practicing 12/12 or 16/8 a few days a week. Once you are comfortable, you can follow this method daily.
  1. Regardless of which type of IF method you choose, keep your diet as diverse as possible. Focus on nutrient-dense, whole foods like high-quality protein (organic meats, wild-caught fish, pasture-raised eggs, organic legumes), healthy fats (olives, avocado, organic grass-fed dairy), and lots of fiber (fruits and vegetables).
  1. It can take your body a few days to adjust to new changes. Pay attention to how you feel after the first week and decide how you want to move forward from there. Remember to be mindful of your appetite, energy levels, bowel movements, and mood, and talk to your doctor if you have any concerns.

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References

  1. https://www.hopkinsmedicine.org/health/wellness-and-prevention/intermittent-fasting-what-is-it-and-how-does-it-work#:~:text=These%20include%20a%20longer%20life,many%20cancers%2C%E2%80%9D%20he%20says.
  2. Malinowski B, Zalewska K, Węsierska A, Sokołowska MM, Socha M, Liczner G, Pawlak-Osińska K, Wiciński M. Intermittent Fasting in Cardiovascular Disorders—An Overview. Nutrients. 2019; 11(3):673. https://doi.org/10.3390/nu11030673
  3. Mohammad Bagherniya, Alexandra E. Butler, George E. Barreto, Amirhossein Sahebkar. The effect of fasting or calorie restriction on autophagy induction: A review of the literature. Ageing Research Reviews, Volume 47, 2018. Pages 183-197, ISSN 1568-1637. https://doi.org/10.1016/j.arr.2018.08.004.
  4. Hoddy, K.K., Marlatt, K.L., Çetinkaya, H. and Ravussin, E. (2020), Intermittent Fasting and Metabolic Health: From Religious Fast to Time-Restricted Feeding. Obesity, 28: S29-S37. https://doi.org/10.1002/oby.22829
  5. Grajower MM, Horne BD. Clinical Management of Intermittent Fasting in Patients with Diabetes Mellitus. Nutrients. 2019 Apr 18;11(4):873. doi: 10.3390/nu11040873. PMID: 31003482; PMCID: PMC6521152.
  6. https://pubmed.ncbi.nlm.nih.gov/29159583/
  7. https://pubmed.ncbi.nlm.nih.gov/34579056/
  8. https://www.sciencedirect.com/science/article/abs/pii/S193152441400200X
  9. https://pubmed.ncbi.nlm.nih.gov/12724520/
  10. https://pubmed.ncbi.nlm.nih.gov/31002478/ 
  11. https://pubmed.ncbi.nlm.nih.gov/29754952/
  12. https://www.mdpi.com/2073-4409/7/5/37 
  13. https://www.ncbi.nlm.nih.gov/labs/pmc/articles/PMC3946160/ 
  14. https://pubmed.ncbi.nlm.nih.gov/19793855/

About the author

Rebecca Washuta is a licensed dietitian with degrees in neuroscience and nutrition and helped individuals develop long-term health habits and achieve various wellness goals.

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