Fat has often been demonized in the diet world, especially during a caloric deficit known as a 'cut.' The high calorie density of fat (9 calories per gram compared to 4 for protein and carbs) makes it an easy target for reduction when trying to shed pounds. However, fats are a vital macronutrient with essential roles in the body. Cutting your fat intake too low can derail your progress and negatively impact your health.
The dangers of cutting fat too low
Adhering to an extremely low-fat diet for an extended period can lead to several adverse health effects. For those attempting to preserve muscle mass, such as bodybuilders, this can be particularly problematic.
- Hormonal Imbalances: Fat is a precursor for the production of several crucial hormones, including testosterone and estrogen. A significantly low-fat intake has been shown to lower testosterone levels, even with adequate protein and carbs. For women, this can disrupt the menstrual cycle.
- Malabsorption of Fat-Soluble Vitamins: Your body requires dietary fat to absorb fat-soluble vitamins: A, D, E, and K. A fat deficiency can lead to inefficient absorption, potentially causing deficiencies that affect skin health, immunity, vision, and more.
- Compromised Immune Function: Severely restricting fat intake can weaken your immune system, making you more susceptible to frequent illnesses and triggering systemic inflammation.
- Skin and Hair Issues: Fat plays a key role in the structure of skin cells and hair follicles. Insufficient fat can result in dry, flaky skin and hair loss.
- Cognitive and Mood Problems: The brain is approximately 60% fat, and essential fatty acids like Omega-3s are vital for brain function and mood regulation. A lack of these fats can lead to poor concentration, irritability, and other mood imbalances.
How to calculate your minimum fat intake
Determining your minimum fat intake depends on individual factors like your lean body mass (LBM) and overall calorie goals. There are two primary methods for calculation.
- Percentage of Total Calories: Health organizations and sports nutritionists recommend that fats make up 20–35% of total daily calorie intake for general health. For athletes and bodybuilders on a cut, this can drop to the lower end, typically 15–20% of total calories. This range allows for higher protein intake while still maintaining essential functions. For example, on a 2,000-calorie diet, a 20% fat intake would be 400 calories (2000 * 0.20), or about 44 grams of fat (400 / 9).
- Gram Per Pound of LBM: A more advanced method is to base intake on your lean body mass (body weight minus fat mass). A general guideline suggests a minimum of 0.25 to 0.3 grams of fat per pound of lean body mass. For a 180-pound person with 10% body fat, their LBM is 162 pounds. A minimum intake at 0.3g/lb LBM would be approximately 49 grams per day (162 * 0.3). Females, due to hormonal differences, may require slightly more, around 0.4g/lb LBM.
Prioritizing protein: a key strategy
During a cutting phase, the priority is to preserve muscle mass while shedding fat. This is primarily achieved through a high protein intake. Protein has a higher thermic effect of food and promotes satiety, which helps with adherence to a calorie-restricted diet. Once your protein target is set (2.3–3.1g/kg of LBM for bodybuilders) and you have a fat baseline (15–20% of calories), carbohydrates fill the remaining calorie budget.
Comparison: Low-Fat vs. Moderate-Fat Cutting Diet
| Feature | Low-Fat (<15% of Calories) | Moderate-Fat (15-25% of Calories) |
|---|---|---|
| Hormonal Impact | High risk of reduced testosterone and hormonal disruption. | Lower risk; helps support hormone production and balance. |
| Satiety & Hunger | Can leave you feeling less full and more prone to cravings, making diet adherence difficult. | Promotes greater satiety, helping to manage appetite and reduce hunger pangs. |
| Nutrient Absorption | Can impair the absorption of essential fat-soluble vitamins (A, D, E, K). | Supports the absorption of fat-soluble vitamins, benefiting overall health. |
| Sustainability | Often difficult to sustain for long periods due to negative side effects and poor satiety. | More sustainable and easier to adhere to, leading to more consistent results. |
| Performance | Can negatively impact energy levels and training performance due to limited energy availability. | Supports training performance by providing a steady energy source. |
Best sources of healthy fats for a cut
Not all fats are created equal. Focus on consuming nutrient-dense sources of healthy, unsaturated fats while minimizing unhealthy saturated and trans fats.
- Avocados: Rich in monounsaturated fats, fiber, and micronutrients.
- Nuts and Seeds: Walnuts, almonds, chia seeds, and flaxseeds provide polyunsaturated fats, including essential Omega-3s.
- Olive Oil: A cornerstone of the Mediterranean diet, extra virgin olive oil is high in monounsaturated fats and antioxidants.
- Fatty Fish: Salmon, mackerel, and sardines are excellent sources of anti-inflammatory Omega-3 fatty acids.
- Nut Butters: Ensure you choose natural versions without added sugars or hydrogenated oils.
Conclusion
When it comes to the minimum amount of fat when cutting, the goal is not to eliminate fat entirely but to find a healthy, sustainable balance that allows for a calorie deficit without sacrificing vital bodily functions. For most individuals, maintaining a fat intake of at least 15-20% of total calories, prioritizing healthy unsaturated sources, and keeping protein high is the optimal strategy. This approach preserves hormonal health, ensures nutrient absorption, and promotes satiety, making the cutting phase more effective and manageable. Avoid the temptation to drastically cut fats, as the short-term weight loss gains are not worth the potential long-term health risks.
For more detailed information on athletic nutrition, consult authoritative resources such as the Nutritional Recommendations for Physique Athletes - PMC.
The importance of satiety in a cutting diet
In a cutting phase, managing hunger is often the biggest challenge. This is where healthy fats play a crucial, unsung role. Fats are digested slowly, leading to a sustained feeling of fullness or satiety that can significantly reduce cravings and overall food intake. For instance, a study showed that people who included avocado in their breakfast were less hungry and ate less later in the day. By incorporating healthy fats strategically into meals, you can make your calorie-restricted diet feel more manageable and sustainable, increasing your chances of success. This is a far better approach than cutting fats to extremes and dealing with the constant, grinding feeling of hunger.
