The 8-hour diet (16/8 fasting): how it works, benefits, and risks

There are many diets, including the one known as 8-hour diet, a modality of intermittent fasting 16/8 Created and popularized by David Zinczenko, this method claims that weight loss can be achieved by concentrating all daily meals within a specific time window. Although in some cases, it has even been promised that results can be as high as... 15 kilos in a month without effortIt is important to note that actual results depend on many factors (diet, physical activity, metabolic health, adherence, etc.) and that such high figures are not the norm nor are they guaranteed for everyone.

In the first week it is promised lose weight 4 kilos without having to deprive yourself of anything or radically change your eating habits. It even allows you to take dessert y wine glassesAlthough always in moderation, without excesses and prioritizing a healthy eating pattern.

It's a slightly different diet from the others, as all the food is concentrated within a range of 8 hours in a rowIt's easy and relatively simple to follow as long as we adapt to that lifestyle. The secret lies in consuming food in any quantity (ideally healthy) for only 8 hour consecutive and maintain a period of 16 hour fast in which no calories are ingested.

Ideally, according to Zinczenko's classic version, breakfast should start at 9 a.m. and the last meal at 5 p.m. The remaining 16 hours are when the body performs a process of metabolism. moderate fasting which processes all the food consumed. However, it is now known that the window can be adapted to each person's schedule as long as the 16-hour calorie-free period is respected.

How The 8 Hour Diet Works

When starting the diet, a routine of fasting about 3 days a week If you're a beginner and not used to going several hours without food, many people start by alternating 16/8 fasting days with normal eating days to ease the transition. As your body gets used to it, you can move on to the 16/8 method. protocol 16/8 every dayprovided there are no medical contraindications.

Over time, the number of fasting days is gradually increased until the body adapts to this new schedule. Rapid weight loss is promised initially, but scientific evidence points more towards... moderate reductions when fasting is accompanied by adequate calorie intake. One of its main objectives is separate the first meal, breakfast, from dinnerso that there is a long interval without consuming calories. This allows the body to lower insulin levels and resort to the fat deposits as a source of energy and to promote certain cellular repair processes.

The best thing about the diet is that fits everyoneBecause you can decide which eight hours best suit your lifestyle, work, family situation, or free time. For example:

Window from 10:00 to 18:00: very popular with those who prefer to eat something before working and have dinner early.
Window from 12:00 to 20:00: a common option for those who get up late or have a social life in the afternoon and evening.
Window from 9:00 to 17:00: very much in line with the original proposal of the 8-hour diet and with circadian rhythms.

During the 16-hour fast, drinking is permitted. water, infusions o just coffeeAlways sin azúcarNo milk or high-calorie drinks. Very light broths are also acceptable, provided they don't provide significant energy. Alcoholic beverages, sugary sodas, and energy drinks are prohibited, as they would break the metabolic fast.

The diet's promoter, Zinczenko, claims that if the diet is followed correctly, You hardly ever go hungry After 5 or 6 in the evening, as the body learns to better manage its reserves, appetite hormones (such as) stabilize. Leptin and ghrelinand fat metabolism is accelerated. In practice, some people may experience hunger, irritability, or lack of concentration during the first few days, but these symptoms usually subside as the body adapts to the fasting pattern.

What happens in the body during 16 hours of fasting

During fasting hours the body stops receiving energy from food and begins to use its available reserves. In the first few hours, it mainly uses the circulating glucose and the glycogen stored in the liver and muscles. As hours pass without eating, the levels of insulin decrease and the body increases its use of body fat as an energy source.

This fuel change favors the fat burning, can improve the insulin sensitivity and has been associated with a better metabolic health in some studies. Furthermore, prolonged fasting stimulates processes of autophagy, a cellular “self-cleaning” mechanism by which damaged components are recycled, which could have positive effects at the cellular level and on long-term health.

If you consistently fast for 16 hours every day, you may observe changes such as better appetite management, certain reduction of inflammation systemic improvements in parameters such as triglycerides or cholesterol in some cases and, in combination with exercise, a loss of body fat. However, these potential benefits depend largely on the diet quality in the 8-hour window, the level of physical activity, sleep, and stress.

Recommended foods in the 8-hour diet

The diet does not strictly restrict foods, but it does recommend a list to help lose weight faster and take care of your metabolic health. Simply reducing meal times isn't enough: choosing foods with high nutritional densityRich in fiber, quality protein, and healthy fats. You can create your own menu by choosing foods that are low in fat and high in protein and fiber.

ProteinsEggs, lean meats (chicken, turkey, rabbit, lean cuts of beef), white and oily fish. proteins They help preserve muscle mass and increase the feeling of satiety.
DairyLow in fat and added sugars. Skimmed milk, unsweetened fortified plant-based drinks, natural or skimmed yogurts, low-fat fresh cheese or cottage cheese.
Seeds and nutsNuts, pistachios, almonds, hazelnuts, chia seeds, flax seeds, or pumpkin seeds. They provide healthy fatsThey contain fiber and minerals, and are a good addition to salads or as a snack within the eating window.
Whole grainsWholemeal bread, oats, brown rice, quinoa, bulgur, or wholemeal pasta. Its content in fiber It helps control appetite and stabilize glucose.
Fruits, vegetables and all greensThese should be added daily, prioritizing leafy green vegetables, cruciferous vegetables (broccoli, cauliflower, cabbage), a variety of vegetables, and fresh seasonal fruits. They provide Vitamins, minerals and essential antioxidants.
Healthy fatsExtra virgin olive oil, avocado, oily fish, nuts, and seeds. These fats promote cardiovascular health and improve satiety.

On the other hand, it is advisable to limit ultra-processed foods as much as possible. added sugarsRefined flours, trans fats, and alcohol. Regularly including these products during the 8-hour fasting period can negate the benefits of fasting and even contribute to weight gain.

Benefits of the 8-hour diet and 16/8 intermittent fasting

The cravings If done correctly and with satiating foods, hunger hormones are better regulated.
The creator ensures that it prevents Heart problems and diabetesSeveral studies suggest that eating dinner very late and overeating at night may be associated with poorer metabolic health, so concentrating food intake during the day could be beneficial.
Promote a Healthy Living by forcing people to plan meals better, reduce constant snacking, and become more aware of what they eat.
Take the fast as a premise and as a good habit for the body to function correctly, facilitating cellular repair processes and improving certain inflammatory markers.
It can be resumed if you stop for a couple of days, as it is a flexible protocol that allows adaptation to social events or changes in routine.

In addition, some studies on 16/8 intermittent fasting point to potential benefits such as:

Moderate weight loss by reducing the meal window and, indirectly, total calorie intake.
Better glucose control and insulin sensitivity in people with mild insulin resistance.
Reduction of inflammation low-grade associated with chronic diseases.
Possible positive effects at the level cognitive and cardiovascular health, although the research is still ongoing and the results are not definitive.

Some proponents of the diet claim that, when used correctly, it can reduce yo-yo effect after periods of weight loss because it promotes stable schedule habits; however, this depends on maintaining a balanced and sustainable diet in the long term, and the scientific evidence on preventing the yo-yo effect is not yet conclusive.

Risks, contraindications, and who shouldn't do the 8-hour diet

While the 8-hour diet can be a helpful tool for many people, it's not suitable for everyone. During the first few days, you may experience some discomfort. intense hungerHeadache, dizziness, irritability, difficulty concentrating, or sleep disturbances. If these symptoms are very intense or persist for a long time, it is advisable to seek medical advice. adjust the protocol or consult a healthcare professional.

In general, 16/8 intermittent fasting is discourages or should only be done under professional supervision in the following cases:

Pregnancy and breastfeeding.
Children, adolescents and frail elderly people.
People with under weight or involuntary weight loss.
Patients with Eating disorder (anorexia, bulimia, binge eating).
People with medicated diabetes or complex metabolic diseases without medical supervision.
People with high sports demand or very intense training that requires a specific nutritional strategy.
Situations of stress or anxiety high levels, in which fasting could worsen the relationship with food.

For those who can practice it, it is essential that the diet be balancedthat covers all the needs of macronutrients y micronutrientsand that it is complemented with regular physical activity and a good night's sleep.

Practical tips for starting the 8-hour diet

It is recommended to start each day with a big glass of water To rehydrate your body after the night, and if possible, walk for at least 10 minutes, jog gently, or do some light exercise each morning to activate your body and boost fat burning. During the day, drink as much water as possible to avoid dehydration and help control hunger.

Some additional recommendations for implementing the 8-hour diet sustainably are:

Choose a feeding window realistic, adapted to your work, family and social schedule.
Advance in a way progressive: start with 12-hour fasts and gradually increase to 16 hours if the body tolerates it well.
prioritizing complete meals Within the window: main dish with protein, vegetables and a source of complex carbohydrates, instead of relying on snacks.
Do not compensate for fasting with Binge nor overindulge in fatty and sugary foods during the 8 hours.
Being flexible at specific social events, resuming the 16/8 pattern the next day without guilt.

As an eating strategy, the 8-hour diet can help many people better regulate their meal times, reduce constant snacking, and promote weight loss, provided it is accompanied by a quality food and respect the situations in which fasting is not indicated.