Why might extremely low-fat diets be challenging to follow?

December 20, 2025 •

4 min read

Studies have shown that very-low-fat diets, where fat constitutes less than 10% of daily calories, are often associated with poor long-term adherence. So, why might extremely low-fat diets be challenging to follow, and what are the hidden drawbacks that make them so difficult to maintain?

Quick Summary

Extremely restrictive fat intake can be difficult to sustain long-term due to issues with satiety, nutrient absorption, and mental and hormonal health, often leading to cravings and non-compliance.

Key Points

Lack of Satiety: Fat provides a crucial sense of fullness, and its severe restriction often leads to persistent hunger and cravings, making adherence difficult.
Nutrient Malabsorption: A very low-fat diet impairs the body's ability to absorb essential fat-soluble vitamins (A, D, E, K), leading to potential deficiencies.
Hormonal Imbalances: Healthy fats are necessary for the synthesis of key hormones, and a very low intake can disrupt balance, affecting reproductive health and metabolism.
Negative Mental Health Effects: Low-fat diets have been linked to an increased risk of anxiety and depression due to impacts on brain function and neurotransmitter production.
Increased Reliance on Unhealthy Carbs: To compensate for flavor and texture, processed low-fat foods often contain added sugars and refined carbohydrates, triggering blood sugar crashes and further cravings.
Sustainability Issues: Due to the combined physiological and psychological difficulties, extremely low-fat diets have a very low long-term adherence rate.

For decades, low-fat diets were the standard recommendation for weight loss and heart health, but extremely restrictive versions—containing less than 10% of daily calories from fat—have proven unsustainable for many. While moderate fat reduction can be healthy, extreme restriction often creates physiological and psychological challenges that make adherence extremely difficult. Understanding these hurdles is crucial for anyone considering this dietary approach.

The Problem with Satiety and Cravings

One of the most immediate and impactful challenges of an extremely low-fat diet is a lack of satiety, or the feeling of fullness and satisfaction after a meal. Fat is digested slowly, helping to signal fullness and keep you feeling full longer. When fat is severely limited, meals can feel less satisfying, leading to several issues:

Increased Hunger: Without the satiating effect of fat, individuals often find themselves feeling constantly hungry, leading to a preoccupation with food. This perpetual state of hunger makes sticking to the diet’s calorie limits and food choices incredibly difficult.
Higher Carbohydrate Consumption: Food manufacturers often replace fat in products with sugar, refined carbohydrates, and other additives to improve flavor and texture. A focus on processed 'low-fat' foods can inadvertently lead to an excessive intake of these carbohydrates, which digest quickly and can cause blood sugar spikes and subsequent crashes. This cycle creates more cravings and hunger, particularly for unhealthy, sugary snacks.
Reduced Food Palatability: Fat contributes significantly to the flavor and enjoyment of food. Without it, meals can taste bland and unappealing, making adherence a chore rather than a satisfying experience. This psychological dissatisfaction can quickly lead to frustration and diet abandonment.

Nutrient Deficiencies are a Major Risk

Extremely low-fat diets pose a significant risk for nutrient deficiencies, as certain vitamins rely on fat for proper absorption and essential fatty acids are eliminated from the diet.

Fat-Soluble Vitamin Malabsorption: Vitamins A, D, E, and K are fat-soluble, meaning they require dietary fat for the body to absorb and utilize them effectively. Without adequate fat intake, deficiency in these crucial vitamins can occur, impacting everything from vision (Vitamin A), bone health (Vitamin D), and immune function (Vitamins A, E, K).
Essential Fatty Acid Deficiency: The body cannot produce essential omega-3 and omega-6 fatty acids, so they must be obtained through food. These are vital for brain function, hormone production, and reducing inflammation. Depriving the body of these fats can lead to dry skin, hair loss, and compromised cognitive function.
Compromised Gut Health: Emerging research suggests a correlation between healthy fats and a balanced gut microbiome. An extremely low-fat diet may disrupt this delicate balance, potentially leading to gastrointestinal issues and a weakened immune system.

Psychological and Hormonal Impacts

The challenges of very low-fat diets extend beyond just the physical. They can have a notable impact on mental and hormonal health, making them emotionally and physically taxing.

Mental and Cognitive Effects

Research has linked very low fat consumption to increased levels of depression and anxiety. The brain is composed largely of fat, and inadequate intake of essential fatty acids can impair nerve-cell membranes and disrupt neurotransmitter function, including that of serotonin. Symptoms can include:

Mood Swings: Imbalanced neurotransmitters can lead to irritability and increased anxiety.
Brain Fog: A lack of healthy fats, particularly omega-3s, can impair cognitive function, leading to difficulty concentrating and reduced mental clarity.
Fatigue: Restrictive low-fat diets often result in insufficient calorie intake and poor nutrient absorption, leading to chronic fatigue.

Hormonal Imbalances

Fat is a critical building block for many hormones, including sex hormones like estrogen and testosterone. Very low-fat diets can disrupt hormonal balance, with potential consequences including:

Irregular Menstrual Cycles: In women, severe fat restriction can lead to irregular or absent periods and fertility issues.
Decreased Testosterone: In men, low fat intake can negatively affect testosterone levels.
Impaired Thyroid Function: Long-term adherence to a very low-fat and high-carbohydrate diet can put stress on the body, potentially impacting thyroid function.

Comparison: Very Low-Fat vs. Balanced Diet


Feature	Very Low-Fat Diet (<10% Fat)	Balanced Diet (20-35% Fat)
Satiety	Poor; often leads to constant hunger and cravings.	Good; healthy fats contribute to feeling full and satisfied.
Nutrient Absorption	Compromised; limits absorption of fat-soluble vitamins (A, D, E, K).	Optimal; supports the absorption of essential vitamins.
Mental Health	Potential negative impacts; linked to increased anxiety, depression, and brain fog.	Supportive; adequate healthy fats are crucial for brain function and mood.
Hormone Balance	Risk of disruption; can affect sex hormone production and thyroid function.	Optimal; provides necessary building blocks for hormone synthesis.
Food Choices	Often bland and restrictive; heavy reliance on processed low-fat products.	Enjoyable and diverse; includes whole foods with healthy fats like nuts, seeds, and avocados.
Sustainability	Low; high rates of attrition due to restrictive nature and side effects.	High; focuses on whole foods and a balanced approach, promoting long-term adherence.

Conclusion

While the concept of extreme fat restriction may seem like a direct path to weight loss, the science and experience of many individuals suggest it is a highly challenging and often unsustainable approach. The physiological and psychological side effects—from persistent hunger and nutrient deficiencies to mood disorders and hormonal imbalances—create a difficult environment for long-term adherence. Instead of demonizing fat, a more sustainable and healthier strategy involves a balanced dietary approach that focuses on whole, minimally processed foods, and includes healthy fats in moderation. Prioritizing overall dietary quality rather than focusing on the extreme restriction of a single macronutrient is a more reliable and enjoyable path to lasting health and wellness.

For more information on structuring a balanced diet, consult guidelines from organizations like the World Health Organization.

Frequently Asked Questions

An extremely low-fat diet, also referred to as a very-low-fat or ultra-low-fat diet, is one where fat constitutes less than 10% of your total daily caloric intake.

Such diets have been linked to increased risks of depression and anxiety because fat is a vital component of the brain's structure and function. Inadequate intake of essential fats can impair neurotransmitter activity, including serotonin function, which regulates mood.

It is very difficult to absorb adequate amounts of fat-soluble vitamins (A, D, E, and K) on a very low-fat diet because they require dietary fat to be properly absorbed by the body. This can lead to various health issues over time.

While short-term weight loss is possible due to calorie restriction, studies show that very low-fat diets are often no more effective than other diet types for long-term, sustained weight loss. The risk of high-sugar, high-carb low-fat processed foods can even counter weight loss goals.

Common physical side effects include constant hunger, fatigue, dry skin, hair loss, constipation, and hormonal imbalances affecting reproductive health.

When fat is removed from processed foods, manufacturers often replace it with sugar and refined carbohydrates to maintain flavor and texture. This can lead to blood sugar spikes and crashes that trigger increased hunger and cravings for more carbs.

A more balanced approach, like a Mediterranean-style diet, emphasizes healthy fats from sources like olive oil, nuts, and fish alongside whole grains, fruits, and vegetables. This provides better satiety, nutrient absorption, and long-term sustainability.