Could Eating Too Little Be Holding You Back?
Undereating Can Backfire
Eating too little can actually work against body composition goals. This is a common experience I see from clients in my clinic, and I completely understand the frustrations for them. They have reduced their food intake, and increased their movement or exercise, but are not seeing the changes they are hoping for. If this sounds familiar, you are not alone. Importantly, the answer is rarely to 'eat less and move more'. In fact, under-fuelling your body is one of the most significant barriers to optimising your body composition.
Let me break down why.
Your Body Is Smart
The human body is an extraordinarily adaptive system. When energy intake drops too low, the body interprets this as a threat to its survival. In response, it initiates a cascade of metabolic and hormonal adaptations designed to preserve energy and protect the body's vital functions.
This is sometimes called 'metabolic adaptation', 'adaptive thermogenesis' or, more simply put 'starvation mode'.
What Happens To Your Body When You Under-Fuel
When the body senses a significant energy deficit over time, several important things happen:
Metabolic rate slows down. The body reduces its basal metabolic rate (BMR) to compensate for the lowered energy intake. BMR is the energy your body expends at rest, or what is needed to maintain basic life process, such as your heart pumping blood around your body, breathing, cell growth and repair. This downregulation therefore reduces your total energy expenditure.
Muscle mass is sacrificed. Without enough protein and overall energy to rely on, your body turns to its own muscle tissue to break down as a source of fuel. Since muscle is a metabolically active tissue, losing more of it can further reduce your metabolic rate, creating a compounding cycle that makes it even harder to shift body fat over time.
Hormones shift unfavourably. Chronic under-fuelling may elevate cortisol levels (a stress hormone), which promotes fat storage, particularly around the mid-section. At the same time, levels of leptin (a hormone that signals satiety and supports metabolic rate) drop, while ghrelin (a hunger hormone) rises. Hello to being hangry!! Thyroid hormone production, which regulates metabolism, may also decline.
Non-exercise activity is reduced. Your body, sensing the energy deficit, unconsciously moves less during the day to help compensate.
Fat storage is prioritised. The body now becomes more efficient at storing fat when food is available. This is an evolutionary survival mechanism. And the exact opposite of what many people are trying to achieve.
Exercise performance and recovery suffer. Without enough energy, it becomes harder to train, recover as well, or build lean muscle effectively. This undermines the very activities that help to support a healthy body composition.
The Flaw in 'Eat Less, Move More'
The oversimplified 'eat less, move more' approach fails to account for the body's dynamic regulatory systems. A person underfuelling by eating 5,500 kJ/day is not necessarily in a larger energy deficit than someone eating 8,500 kJ/day. They are in physiological stress. Their body has likely already compensated by reducing its energy output to match.
This is why chronic dieters may find their results plateauing or even reversing over time. A restrictive approach may provide short-term results, but it is not a sustainable strategy for lasting body composition change.
How to Fuel Strategically
Optimising body composition is not about eating as little as possible. It is about eating the right amount of the right foods to support your metabolic health, lean muscle retention, and sustainable fat reduction. Here is what that looks like in practice:
Eat enough to support your metabolism. Individual needs vary considerably based on your height, weight, physical activity level, age, and health status. Working with a Certified Practicing Nutritionist can help to support you to understand your specific requirements.
Prioritise protein. Adequate protein intake helps to preserve muscle mass, supports satiety, and has a higher thermic effect, which means that the body burns more energy digesting it than it does for fats or carbohydrates.
Do not fear carbohydrates. Carbohydrates are the body's preferred fuel source, particularly for the brain and during exercise. We need a certain amount to function optimally. Whole food sources such as oats, legumes, fruit, and starchy vegetables provide sustained energy and support thyroid and hormonal health.
Eat consistently throughout the day. Skipping meals may lead to overeating later in the day, or a tendency to reach for those foods that may provide quick energy with minimal nutrition. Regular, balanced meals help to stabilise blood sugar levels as well as your appetite regulation hormones.
Support your gut and overall nutritional status. Micronutrient deficiencies, particularly in iron, zinc, magnesium, iodine, and B vitamins, can affect energy metabolism, thyroid function, and exercise recovery, all of which influence body composition outcomes.
The Takeaway
If you have been eating very little and feel like your body is 'stuck,' it may be time to consider whether under-fuelling is working against you. Sustainable body composition change requires a well-nourished, well-supported metabolism. Not one that is running on empty.
Food is not the enemy. It is the very thing your body needs to function, heal, and change. Eating enough, strategically and consistently, is one of the most powerful things you can do to work with your physiology rather than against it.
Are you ready to take the guesswork out of your nutrition? Why not consider booking in a consultation with Katie to get personalised support tailored to your body composition goals. By tracking your food intake and movement through Easy Diet Diary, which syncs directly with Katie's analysis software (FoodWorks), she can help to build recommendations around your unique energy requirements, nutrient needs, and individual goals.
Are you looking for someone to support you with your 2026 health and wellness goals?
Consider booking in a 1:1 Clinical Nutrition appointment where together we can develop a personalised nutrition plan that supports your unique health goals. This incorporates dietary and lifestyle recommendations, and practitioner-only supplements where clinically indicated.
Katie practices at: Uprise Health, 136 Lennox Street, Richmond, 3121, Victoria.
Appointments: Face-to-face and Telehealth available (Australia wide)
Contact: admin@katiehopcraft.com.au
If you have any questions or need personalised guidance, feel free to reach out.
The information provided in this blog is for your personal or other non-commercial, educational purposes. It should not be considered as medical or professional advice. We recommend you consult with a GP or other healthcare professional before taking or omitting to take any action based on this blog. While the author uses best endeavours to provide accurate and true content, the author makes no guarantees or promises and assumes no liability regarding the accuracy, reliability or completeness of the information presented. The information, opinions, and recommendations presented in this blog are for general information only and any reliance on the information provided in this blog is done at your own risk.