Nutrition Diet: What to do if your body fat is low?

October 21, 2025 •

4 min read

While obesity is a well-publicized health concern, a significant body of research confirms that having excessively low body fat also poses serious health risks. If your body fat is low, it's crucial to address it with a strategic, healthy approach rather than resorting to empty calories, focusing on sustainable weight gain and overall well-being.

Quick Summary

This guide outlines safe and effective strategies for increasing body fat and building muscle mass through a nutrient-dense diet, the strategic inclusion of healthy fats, and a focus on targeted resistance training, while avoiding unhealthy weight gain methods.

Key Points

Understand the Risks: Low body fat can cause serious health issues like hormonal imbalances, a weakened immune system, and nutrient deficiencies.
Create a Calorie Surplus: Consume 300 to 500 extra calories per day from nutrient-dense sources to promote healthy weight gain.
Prioritize Healthy Fats and Protein: Incorporate healthy fats from nuts, seeds, avocados, and oily fish, and ensure adequate protein for muscle building.
Engage in Strength Training: Implement resistance training and compound movements to build muscle mass, not just fat.
Focus on Meal Timing and Frequency: Eat smaller, more frequent meals and snacks to increase overall caloric intake without feeling overly full.
Consult a Professional: If you have low body fat due to an underlying condition, or if weight gain is a challenge, seek guidance from a doctor or dietitian.

Understanding the Risks of Low Body Fat

For many, low body fat seems like a fitness goal, but critically low levels can disrupt standard physiological systems and lead to health complications. Adipose tissue (fat) is vital for several bodily functions, including hormone regulation, energy storage, and insulating organs. When these levels drop too low, you may experience a variety of health issues.

Potential Consequences of Insufficient Body Fat

Hormonal Imbalances: In women, very low body fat can disrupt hormonal balance, leading to irregular or absent menstrual cycles (amenorrhea). For men, testosterone levels can plummet, resulting in muscle loss and fatigue.
Weakened Immune System: Insufficient fat can compromise the immune system, making you more susceptible to infections and slowing recovery times.
Fatigue and Low Energy: As one of the body's primary energy reserves, low body fat means less stored energy, which can lead to constant tiredness and weakness.
Nutrient Deficiencies: Fat is essential for absorbing fat-soluble vitamins (A, D, E, and K). Too little fat can cause deficiencies that impact vision, bone health, and immune function.
Heart and Brain Function: Healthy fats are crucial for heart health and cognitive function. A deficit can impair concentration and mood, and in extreme cases, affect heart rhythm.

The Nutritional Strategy for Healthy Weight Gain

The core principle for gaining weight is to consume more calories than you burn, creating a caloric surplus. However, the quality of these calories is paramount to ensure you gain healthy muscle and fat, not just empty-calorie fat. Aim for an increase of 300 to 500 calories per day to facilitate gradual, sustainable weight gain.

Prioritizing Nutrient-Dense Foods

Instead of relying on sugary snacks and fast food, focus on whole foods that provide ample nutrients and energy. This is especially important for those with low body fat, who may also have low muscle mass and poor nutrient absorption.

Healthy Fats: Calorie-dense and crucial for hormonal and cellular health, healthy fats should be a priority. Sources include avocados, nuts (almonds, cashews, walnuts), seeds (flax, chia, sunflower), nut butters, olive oil, and fatty fish like salmon.
Protein: Essential for building and repairing muscle tissue. Incorporate lean meats, eggs, dairy, and legumes into your diet. Protein supplements like whey or casein can also be beneficial, particularly post-workout.
Complex Carbohydrates: Fuel your body and workouts with complex carbs like brown rice, oats, quinoa, sweet potatoes, and whole-grain breads.

Incorporating Strength Training to Build Muscle

Simply eating more calories without a proper exercise regimen can lead to unwanted fat gain rather than muscle mass. Resistance training is key to directing the caloric surplus towards building muscle through a process called hypertrophy.

Types of Exercises to Focus On

Compound Movements: Exercises that involve multiple muscle groups, such as squats, deadlifts, and bench presses, are highly effective for stimulating overall muscle growth.
Progressive Overload: To continue gaining strength and size, you must progressively increase the intensity of your workouts by lifting heavier weights, increasing reps, or reducing rest time.

The Importance of Rest

Adequate rest is just as important as the training itself. Your muscles grow and repair during rest periods, so aim for sufficient sleep and avoid overtraining.


Feature	Resistance Training (Weightlifting)	Cardiovascular Exercise (Cardio)
Primary Goal for Weight Gain	Building and maintaining lean muscle mass, increasing metabolic rate.	Maintaining heart health and endurance, but can burn excess calories.
Energy Source Priority	Uses stored glycogen in muscles for intense, short-duration activity.	Primarily uses stored fat for longer, sustained activity.
Recommended Frequency	At least two to three non-consecutive days per week, targeting major muscle groups.	Important for overall health; can be limited to shorter sessions (e.g., 20 mins, 3 times per week) to avoid excessive calorie burn.
Intensity	High intensity, focusing on lifting heavier loads to fatigue.	Moderate intensity for steady-state, or high-intensity intervals (HIIT).

Sample Nutrition and Exercise Plan Framework

A Day of Nutrient-Dense Eating

Breakfast: Oatmeal made with whole milk, topped with nuts, seeds, and dried fruit.
Snack: Full-fat Greek yogurt with a handful of trail mix.
Lunch: Lean protein (chicken, fish), brown rice, and steamed vegetables with a drizzle of olive oil.
Snack: Smoothie with whole milk, banana, nut butter, and whey protein.
Dinner: Fatty fish (salmon) or lean red meat, sweet potato, and avocado salad.
Pre-Bed Snack: Cottage cheese or a handful of nuts to provide a slow-digesting protein source.

Incorporating Physical Activity

Monday: Full-body resistance training session, focusing on compound lifts.
Tuesday: Rest or light cardio (e.g., a brisk walk).
Wednesday: Full-body resistance training session.
Thursday: Rest or light cardio.
Friday: Full-body resistance training session.
Weekend: Active recovery, stretching, or light exercise. Ensure adequate sleep each night for muscle repair.

Conclusion: A Holistic Approach to Health

Addressing low body fat is not about a quick fix but about adopting a sustainable, holistic approach to nutrition and fitness. By understanding the health risks of insufficient body fat and prioritizing nutrient-dense foods, adequate calorie intake, and a consistent strength training routine, you can safely and effectively increase your body fat and muscle mass. Combining a balanced diet with proper exercise and rest is the most reliable path to achieving a healthier, more robust physique. Remember, health is not just about weight or body fat percentage but about a robust, functional body.

For additional support and guidance, consult with a healthcare professional or a registered dietitian to create a personalized plan.

Resources

NHS Guide to Healthy Weight Gain: https://www.nhs.uk/live-well/healthy-weight/managing-your-weight/healthy-ways-to-gain-weight/

Frequently Asked Questions

Healthy body fat ranges vary by age and gender. For instance, the American College of Sports Medicine suggests athletic women can have as low as 10% body fat, while men can have as low as 3%, but for general health, slightly higher percentages are often recommended.

While junk food is high in calories, it lacks essential nutrients. Gaining weight this way can increase your risk of chronic diseases and won't build healthy muscle mass, which is a key component of healthy weight gain.

A healthy rate of weight gain is gradual and steady. A reasonable goal is to gain 1-2 pounds per week by maintaining a modest calorie surplus.

The term 'skinny fat' refers to having low lean muscle mass despite a relatively low body weight. The strategy is to increase both muscle and fat mass through resistance training and a high-protein, calorie-dense diet, focusing on nutrient-rich foods.

While some supplements, like whey protein, can be helpful, most of your nutritional needs can and should be met through whole foods. Relying on whole foods ensures a broader range of nutrients and is a safer approach than unverified supplements.

Strength training is crucial for building muscle and promoting healthy weight gain, while excessive cardio can burn too many calories and hinder your progress. Incorporate strength training regularly and keep cardio sessions shorter or less frequent if weight gain is the primary goal.

It's best to consult a doctor if your weight loss is unexplained or you lose more than 5% of your body weight in 6-12 months. A medical professional can rule out underlying conditions and help you plan a healthy and safe weight gain strategy.