Dirty fasting, also known as dirty keto, has become a popular dieting trend in recent years. But what exactly is dirty fasting and does it really help with weight loss? Here is an in-depth look at what dirty fasting is, how it works, its benefits and downsides, and whether it’s an effective approach for weight loss.
What is Dirty Fasting?
Dirty fasting is a variation of intermittent fasting that incorporates a ketogenic or low-carb diet on the fasting days. Like other forms of intermittent fasting, dirty fasting involves alternating between fasting and eating periods. On fasting days, dirty fasters drastically reduce their calorie intake. But unlike a pure fast where only water, coffee, or tea is allowed, dirty fasters also consume high fat foods like fatty meats, eggs, nuts, seeds, and low-carb vegetables.
The term “dirty” refers to allowing foods outside of pure water, coffee, and tea during the fasting windows. However, the foods allowed on dirty fasting days still align with ketogenic dieting by being very low in carbs and high in fat. The goal is to get the body into a state of ketosis, where it burns fat rather than carbs for fuel.
Typical Dirty Fasting Schedule
There are several variations, but a typical dirty fasting schedule would look something like this:
- Fasting days: Consume 500-600 calories from high fat, low carb foods within a 4-8 hour eating window. The remaining 16-20 hours are the fasting period.
- Non-fasting days: Eat a regular ketogenic diet, staying under 50g net carbs. Some dirty fasters will eat a “normal” diet on these days instead of keto.
- Frequency: Dirty fasting schedules vary from every other day to 4-5 days per week of fasting.
Foods Allowed on Fasting Days
Here are some examples of foods that are acceptable to eat on dirty fasting days:
- Meat: Fatty cuts like bacon, pork belly, ribeye steak, chicken thighs
- Eggs
- Full fat dairy: Butter, heavy cream, cheese
- Nuts and seeds
- Non-starchy vegetables: Leafy greens, broccoli, cauliflower, peppers
- Avocados and olives
- Condiments: Salt, pepper, oils, mustard, hot sauce
Foods to Avoid on Fasting Days
Foods that should be avoided on dirty fasting days include:
- Grains: Bread, pasta, rice, cereal
- Beans and legumes
- Starchy vegetables: Potatoes, sweet potatoes, corn
- Fruit
- Sugar and sweets
- Beer, wine, and sweetened drinks
How Does Dirty Fasting Work for Weight Loss?
Dirty fasting promotes weight loss in two key ways:
1. Calorie Restriction
On fasting days, dirty fasters consume a fraction of their normal calorie intake, usually around 500-600 calories. This severe calorie restriction forces the body to burn through glycogen (stored glucose) and then start accessing and burning its fat stores for fuel. Burning more fat than you consume is the basic formula for all weight loss.
2. Ketosis
By consuming very low carb, high fat foods on fasting days, dirty fasters aim to get into ketosis. This is a metabolic state where the body switches from primarily burning carbs to primarily burning fat and ketones for fuel. Ketosis allows your body to more efficiently access and burn its stored body fat.
Achieving ketosis through intermittent fasting and very low carb eating may provide even greater fat burning and weight loss benefits than intermittent fasting alone. However, getting into ketosis requires strict carb restriction and isn’t necessarily guaranteed with dirty fasting.
Benefits of Dirty Fasting
Here are some of the touted benefits of incorporating dirty fasting into your diet routine:
Enhanced Weight Loss
As described above, dirty fasting enhances weight loss through calorie restriction, ketosis, and increased fat burning. Losing weight more quickly can be motivating and lead to greater compliance with intermittent fasting.
Convenience
Eating keto-friendly foods makes dirty fasting more convenient, sustainable, and flexible for many people. Having food options beyond zero-calorie beverages makes the prolonged fasting periods more doable.
Preserves Muscle Mass
Consuming adequate protein from meat, eggs, and dairy on fasting days helps preserve muscle mass as you lose weight. This leads to more fat loss and less muscle loss compared to water fasting.
Improved Satiety
High fat, high protein keto meals provide far more satiety and fullness compared to pure fasting with zero-calorie beverages. This satisfaction can help you make it through fasting periods comfortably.
Boosts Energy on Fasting Days
Getting some calories, fat, and protein on fasting days provides you with steady energy. This makes it easier to stick with your daily activities and workouts on days with reduced food intake.
Supports Ketosis
Consuming very low carb foods enables you to get into ketosis faster and stay there throughout the fasting periods. Ketosis provides unique fat burning and weight loss benefits.
Potential Downsides of Dirty Fasting
Dirty fasting also comes with some potential drawbacks and downsides:
Not as Effective for Weight Loss
While dirty fasting may provide quicker initial weight loss results, over the long term it may not be as effective as clean fasting. Consuming extra calories, carbs, protein, and fat can blunt some of the metabolic benefits of pure fasting.
Risk of Overeating on Non-Fasting Days
The severe calorie restriction of dirty fasting could lead some people to overeat or binge on non-fasting days. This could counteract the calorie deficit and fat loss from the fasting days.
Nutritional Deficiencies
Because of the very limited food intake, dirty fasting increases the risk for potential nutritional deficiencies over time. This includes deficiencies in vitamins, minerals, antioxidants, electrolytes, fiber, and phytonutrients.
GI Issues
Jumping from low calorie, low carb fasting days to higher carb non-fasting days can disrupt digestion and GI function. Many people report constipation, diarrhea, bloating, and indigestion with dirty fasting.
Difficulty Sticking to Keto Diet
Maintaining ketosis through strict low-carb eating is very challenging for some people, especially over the long term. Slipping in and out of ketosis can lessen results.
Keto Flu Side Effects
Transitioning into ketosis can sometimes produce temporary flu-like symptoms for a few days. Symptoms like fatigue, headache, nausea, dizziness, and brain fog can impact daily function.
Is Dirty Fasting Right For You?
Dirty fasting can be worth considering if you:
- Struggle with hunger and need more satiety when fasting
- Experience low energy, brain fog, or lightheadedness when fasting
- Strongly prefer low carb, high fat ketogenic eating
- Have trouble sticking with longer pure fasting periods
- Need convenience and flexibility when intermittent fasting
However, dirty fasting may not be the best fit if:
- You have a history of disordered eating or tendency to binge
- You experience gastrointestinal issues with fasting or keto diets
- You are pregnant, breastfeeding, or have other higher calorie needs
- You have a medical condition that requires special dietary considerations
- You take medications that require food/carb intake
Overall, dirty fasting requires very careful planning to meet nutritional needs while remaining in ketosis. Consult a knowledgeable healthcare practitioner before attempting dirty fasting.
Is Dirty Fasting Healthy Long Term?
Research on dirty fasting is limited, so the long term effects are unknown. Potential concerns with dirty fasting for longer periods include:
- Nutritional deficiencies from restrictive intake
- Higher cholesterol and lipids from excessive saturated fat intake
- Hormonal issues and loss of periods in women from low body fat
- Increased risk of disordered eating patterns
- Difficulty adhering to restrictive keto diet long term
Because of these concerns, it may be best suited for short term use like before a major event or to get over a weight loss plateau. As with any restrictive diet, dirty fasting should be done under medical supervision.
Tips for Successful Dirty Fasting
If you want to give dirty fasting a try, here are some tips to increase your chances of success:
- Ease into dirty fasting slowly – don’t jump straight into full day fasts
- Stay very hydrated by drinking water, herbal tea, broth, etc.
- Get enough electrolytes on fasting days
- Choose fattier cuts of meat and add extra fat like oils, butter, etc.
- Keep carbohydrate counts very low – aim for under 20g net carbs
- Plan ahead for fasting days with grocery shopping and meal prep
- Listen to your body – be prepared to modify as needed
- Consider taking mineral supplements if doing dirty fasting long term
The Bottom Line
Dirty fasting involves intermittent fasting combined with a ketogenic diet on fasting days. This style of fasting allows fatty foods like meat, eggs, and dairy during the prolonged fasting periods. Dirty fasting aims to enhance fat burning through calorie restriction and ketosis. Potential benefits include faster weight loss, increased satiety and energy on fasting days, and flexibility. However, dirty fasting is difficult to maintain long term and risks several nutritional and hormonal deficiencies without medical guidance. Overall, dirty fasting requires very mindful planning and should only be followed short term. People respond very differently, so carefully listen to your body if experimenting with this controversial dietary approach.