Intermittent fasting, or the practice of fasting for a set period, has disrupted the traditional three-meals-a-day mindset and changed the way we think about mealtimes. It is currently one of the most popular health trends, with the 16:8 diet being among the most common.
People are adopting intermittent fasting practices as a strategy to lose weight, improve brain function, and simplify their eating habits and meal plans. But what is the 16:8 intermittent fasting diet, and how do you get started?
What Is 16 8 Fasting?
Intermittent fasting is a dietary pattern that alternates between periods of fasting and eating.
Unlike other diets, fasting plans do not specify what or how much you should eat per day. Instead, they primarily focus on when you should eat. Due to this distinction, intermittent fasting is not considered a diet in the conventional sense. Instead, it may be better described as an eating pattern.
The 16:8 diet is a popular version of intermittent fasting. It involves consuming your meals during an 8-hour eating window while fasting or abstaining from food for the remaining 16 hours a day.
How to Do It
The 16:8 intermittent fasting method, sometimes referred to as the 16 hours fast, restricts your eating to eight hours. This form of intermittent fasting is particularly popular because you spend a large portion of the fasting window asleep.
To get started, begin by selecting the eight hours during which you will consume all of your meals and snacks.
Many people prefer to eat between noon and eight o’clock in the evening, as this means that they only need to skip breakfast, while still eating a typical lunch and dinner.
Some eating windows include:
- 10 am to 6 pm
- 11 am to 7 pm
- 12 pm to 8 pm
When developing your 16:8 plan, you may want to use your current sleep patterns and mealtimes as a guide. For example, if you are an early riser, then you may choose to break your fast around 10 am to avoid excess hours without food intake. Or perhaps your appetite is the greatest at night before bed. If this is the case, then you may decide on a 1 pm to 9 pm window to allow for an evening snack.
Sample 16:8 Fasting Schedule
- 7:00 am Wake up
- 7:30 am Lemon water
- 7:45 am Skip your morning meal
- 12:00 pm Lunch
- 3:00 pm Snack
- 6:00 pm Dinner
- 7:30 pm Snack
- 8:00 pm Begin fast for 16 hours
Foods to Eat
Unlike most diets, 16:8 intermittent fasting does not have any food rules or restrictions. There is no calorie restriction, meaning that you don’t waste time calorie counting or monitoring your intake of carbs. For this reason, many people find that it simplifies their eating habits and allows them to spend less time meal planning.
However, it is still recommended to limit intake of processed and junk foods, as these are associated with weight gain and an increased risk of diseases such as obesity, heart disease, and certain types of cancer.
Even while intermittent fasting, try to focus on healthy food choices which include:
- Fruits and vegetables
- Whole grains and complex carbohydrates: Such as brown rice, oats, barley, quinoa, and more
- Lean proteins: Lean red meat, poultry, fish, beans, tofu, nuts, seeds, and eggs
- Healthy fats: From fatty fish, olive oil, avocados, coconuts, nuts, and seeds
The 16:8 diet allows for calorie-free drinks during the 16-hour fasting period. These include water, unsweetened teas, and black coffee. In addition to preventing dehydration, beverages may also play a crucial role in decreasing hunger cues. Drinking plenty of fluids may help increase feelings of satiety, meaning that you will feel fuller for longer (1).
16:8 intermittent fasting is associated with a number of health benefits, including:
Weight Loss and Difference in Body Composition
The 16:8 diet has become a favored weight loss program among dieters, and for a good reason. There is evidence that intermittent fasting may help you lose weight and boost your metabolism (2, 3). It does this in two ways:
First, fasting makes you eat fewer meals, resulting in decreased calorie intake and food consumption. In general, individuals practicing the 16:8 fast skip breakfast and stop eating at a set time. Therefore, unless you overcompensate by eating much more during meals, you end up consuming fewer calories during the limited 8-hour timeframe.
Additionally, your body also adjusts hormone levels during a fast to make fat stores more accessible (2-6). Basically, when your body is cut off from its preferred sources of energy, namely glucose and glycogen reserves, it will adapt to start burning fat as its primary source of fuel. This means that you are not only losing pounds, but a portion of that weight loss will come from body fat storage.
How much weight can you expect to lose on an intermittent fast? According to a 2014 review article, intermittent fasting was found to reduce body weight by 3 to 8% over 3 to 24 weeks. This study also determined that participants had a 4 to 7% reduction in waist circumference, meaning that they lost belly fat (7).
A different review study found that intermittent fasting may cause a weight loss of 11 to 16% after 12 weeks. Furthermore, researchers noted that intermittent fasting resulted in a lower loss of muscle tissue when compared to typical calorie restriction diets (8).
Decreased Risk of Type 2 Diabetes
Type 2 diabetes develops, in part, due to insulin resistance. Insulin is a hormone that tells the cells of your body to absorb and use blood sugar for energy. In people with insulin resistance, insulin is no longer able to effectively communicate with cells, resulting in chronically high blood sugar.
Research has shown that intermittent fasting may help decrease insulin resistance, improve blood sugar levels, and increase blood sugar control. One review study found that intermittent fasting decreased fasting blood sugar by 3 to 6% and fasting insulin levels by 20 to 31% in people with a diagnosis of prediabetes (7).
These findings indicate that intermittent fasting may be able to benefit people at risk of developing type 2 diabetes.
One of the most exciting theories about fasting is the possibility that it could extend your lifespan. However, much of the science in this area is based on research conducted using animals and not humans.
Animal studies have shown that intermittent fasting increases longevity in rats. One such study found that short-term fasting periods increased the lifespan of female rats (9). In a different study, researchers determined that rats in the intermittent fasting group had an 83% increase in life expectancy compared to those on a regular diet (10).
Keep in mind that animal studies are considered preliminary research, and many questions about this theory still need to be answered using high-quality human studies.
16:8 Fasting Meal Plan Sample
Are you interested in trying the 16:8 diet? Below is a 7-day meal plan that has everything you need to get started. Each day consists of lunch and dinner with snacking between meals.
- Meal #1: Avocado chicken salad
- Snack #2: Handful of mixed nuts with apricot slices
- Meal #3: Macadamia basil pesto pasta
- Snack #4: Glass of red wine and cheese
- Meal #1: Vegan chickpea salad
- Snack #2: Apple slices with peanut butter
- Meal #3: Teriyaki chicken and cauliflower rice
- Snack #4: Mixed berries with coconut cream
- Meal #1: Tuna avocado salad on a whole wheat wrap
- Snack #2: Greek yogurt
- Meal #3: Asian fried noodles
- Snack #4: Two chocolate chip cookies and a glass of milk
- Meal #1: Broccoli tofu salad with quinoa
- Snack #2: Piece of dark chocolate and bowl of mixed berries
- Meal #3: Seared salmon with brown rice and parmesan-kale salad
- Snack #4: Baked apple with cinnamon
- Meal #1: Turkey chili with cornbread
- Snack #2: Organic edamame and almond slices
- Meal #3: Grilled shrimp served with corn and black bean salsa
- Snack #4: Fruit salad with walnuts
- Meal #1: Grilled salmon with brown rice and mixed greens
- Snack #2: Greek yogurt topped with raspberries
- Meal #3: Mexican tempeh quinoa salad
- Snack # 4: Watermelon slices sprinkled with sea salt
- Meal #1: Sprouts, chicken, and quinoa Buddha bowl
- Snack #2: Hummus and pita with raw veggie sticks
- Meal #3: Hearty chicken tortilla soup with garlic bread
- Snack #4: Banana slices dipped in dark chocolate
Side Effects and Safety Concerns
Proponents of intermittent fasting find that it is an effective approach to lose weight and simplify their diet. However, this diet has drawbacks and may not be appropriate for everyone.
As you might imagine, the most common side effect of intermittent fasting is hunger. Additionally, people sometimes report symptoms such as weakness and fatigue during the fasting window, especially when first starting the 16:8 eating plan.
Overeating or binge eating can also occur during the eating window. This may result in weight gain, digestive issues, and unhealthy food habits.
If you are underweight, intermittent fasting may not be the right option for you and could result in harm to your health. Additionally, individuals who have a history of eating disorders may want to avoid intermittent fasting, as this regimen may not provide enough flexibility to support treatment and recovery.
People with underlying medical and health conditions should speak with a healthcare professional before trying the 16:8 diet. This includes anyone who:
- Has diabetes
- Is taking certain medications
- Has low blood pressure
- Is underweight or malnourished
- Has a history of an eating disorder
- Is trying to become pregnant
- Is pregnant or breastfeeding
Furthermore, if you find that you are uncomfortable with the idea of fasting for 16 hours, then the 16:8 diet may not be the best choice for you. Ultimately, there is no one-size-fits-all way to nutrition, and the best diets are the ones that you can maintain for the long run.
How often should you do 16:8 intermittent fasting?
You can repeat the 16:8 cycle as frequently as you would like. Some people may be able to practice this routine every day, while others may decide to only fast once or twice a week. The frequency of your fasts should depend on your personal preference and health goals.
How long does it take for 16:8 intermittent fasting to work?
The answer to this question depends on several factors, including age, gender, genetics, starting weight, fitness level, and extent of caloric deficit (amount of calories cut). In general, an individual will begin to see the results over the course of three to four weeks.
16:8 intermittent fast can be an effective and sustainable way to lose those extra pounds and improve overall wellness when combined with healthy lifestyle choices. These include consuming a diet rich in nutrients, limiting junk food, meeting your fitness needs, and getting enough rest.
Individuals practicing this dietary pattern should focus on eating a variety of whole foods, fruits, veggies, and protein. Hydration is also essential during intermittent fasting and should not be limited to your eating window. Be sure to sip on water and noncaloric beverages, such as tea and coffee, throughout the day to meet fluid needs.
Although 16:8 intermittent fast is considered a safe process for most healthy and well-nourished adults, you may consider speaking with a registered dietitian or doctor before starting any type of intermittent fasting plan.
- Davy, Brenda M., et al. “Water Consumption Reduces Energy Intake at a Breakfast Meal in Obese Older Adults.” Journal of the American Dietetic Association, vol. 108, no. 7, 2008, pp. 1236–1239., doi:10.1016/j.jada.2008.04.013
- Zauner, C et al. “Resting energy expenditure in short-term starvation is increased as a result of an increase in serum norepinephrine.” The American journal of clinical nutrition vol. 71,6 (2000): 1511-5. doi:10.1093/ajcn/71.6.1511
- Mansell, P I et al. “Enhanced thermogenic response to epinephrine after 48-h starvation in humans.” The American journal of physiology vol. 258,1 Pt 2 (1990): R87-93. doi:10.1152/ajpregu.1990.258.1.R87
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- Ho, K Y et al. “Fasting enhances growth hormone secretion and amplifies the complex rhythms of growth hormone secretion in man.” The Journal of clinical investigation vol. 81,4 (1988): 968-75. doi:10.1172/JCI113450
- Hartman, M L et al. “Augmented growth hormone (GH) secretory burst frequency and amplitude mediate enhanced GH secretion during a two-day fast in normal men.” The Journal of clinical endocrinology and metabolism vol. 74,4 (1992): 757-65. doi:10.1210/jcem.74.4.1548337
- Barnosky, Adrienne R., et al. “Intermittent Fasting vs Daily Calorie Restriction for Type 2 Diabetes Prevention: a Review of Human Findings.” Translational Research, vol. 164, no. 4, 2014, pp. 302–311., doi:10.1016/j.trsl.2014.05.013.
- Varady, K A. “Intermittent versus daily calorie restriction: which diet regimen is more effective for weight loss?.” Obesity reviews : an official journal of the International Association for the Study of Obesity vol. 12,7 (2011): e593-601. doi:10.1111/j.1467-789X.2011.00873.x
- Sogawa, H, and C Kubo. “Influence of short-term repeated fasting on the longevity of female (NZB x NZW)F1 mice.” Mechanisms of ageing and development vol. 115,1-2 (2000): 61-71. doi:10.1016/s0047-6374(00)00109-3
- Goodrick, C L et al. “Effects of intermittent feeding upon growth and life span in rats.” Gerontology vol. 28,4 (1982): 233-41. doi:10.1159/000212538