Not Eating Enough to lose weight? Here's how It Could Be Sabotaging Your Weight Loss Goals

An evidence-based guide for people who want real, lasting results

A Message from Me to You; why are we Not eating enough to lose weight?

As a specialist nutritionist and personal trainer in weight management and cancer rehabilitation, I see one common factor with most of my clients — they are not eating enough to lose weight. My client base is predominantly women (though men are absolutely welcome to work with me), and something I’ve observed over and over again is the deeply ingrained cultural message that women should eat less. It's toxic and outdated, yet it still echoes through every corner of the fitness and diet industry.

Even my most intelligent, driven, and thoughtful clients have been unknowingly affected by it. I remember growing up during the height of the ‘heroin chic’ trend, with Kate Moss’s infamous quote “nothing tastes as good as skinny feels” ringing in my ears. As a woman with natural curves, I was never going to look the way fashion told me I should — so I took a different path and found solace at the gym! It’s time to dismantle the damaging belief that eating less is always better — your body deserves more than survival mode.

Now it’s your turn. This article is here to help you break free from the harmful messaging that has been fed to women for generations. The truth is: eating less is not better. You are a living, breathing human being — and your body deserves nourishment, strength, and vitality.

If you’ve gone through something as significant as a cancer journey, giving birth or are recovering from a period of chronic stress or overtraining, your body needs even more care and fuel to rebuild. Let this be the start of you choosing to support yourself — from the inside out.

Understanding Your Body’s Energy Needs

Before we talk about what happens when you eat too little, it’s important to understand how your body uses energy every day.

Basal Metabolic Rate (BMR)

Your BMR is the number of calories your body burns at rest just to keep you alive. It supports basic, essential functions such as:

• Breathing and heartbeat

• Blood circulation

• Brain and nervous system activity

• Hormone production and regulation

• Cell repair and regeneration

• Hair, skin, and nail growth

If you're eating only enough to match your BMR — or less — your body begins prioritising vital functions. Non-essential processes, like healthy hair, skin, nails, and reproductive hormones, are scaled back. This is often why women who under-eat experience fatigue, hair thinning, brittle nails, and menstrual irregularities.

Total Daily Energy Expenditure (TDEE)

Your TDEE is your BMR plus the energy you expend through:

• Exercise and physical activity

• Daily movements (walking, cooking, cleaning)

• Digestion (yes, even eating burns calories)

TDEE is calculated by multiplying BMR by an activity factor (1), as shown below:

Activity Level	Factor
Sedentary	1.2
Lightly active	1.375
Moderately active	1.55
Very active	1.725
Super active	1.9

For example, if your BMR is 1,400 kcal/day and you're moderately active, your TDEE is roughly 2,170 kcal/day. This is the amount of energy you need to maintain your current weight and support all body systems effectively. To lose weight effectively, you need to be in a calorie deficit — but one that’s safe and sustainable, without compromising your metabolism. A moderate reduction of around 300-600 kcal per day can create this deficit without dropping below your BMR, ensuring your body still has enough energy to function well and support your workouts.

The Hidden Cost of Chronic Under-Eating

1. Metabolic Adaptation

When you consistently under-eat, your body responds by slowing down your metabolism — a protective mechanism known as metabolic adaptation. It reduces your resting energy expenditure to conserve energy, making it harder to lose weight over time.

Research by Martin et al. (8) found that individuals on a calorie-restricted diet experienced a notable drop in resting metabolic rate, even when accounting for weight loss. Similarly, Redman and Ravussin (6) reported hormonal shifts and reduced energy output during long-term calorie restriction.

2. Muscle Loss and Physical Weakness

Low calorie intake also reduces your body’s ability to maintain muscle mass. Without enough energy and protein, the body breaks down muscle tissue for fuel — which further slows your metabolism and weakens your overall physique. A study by Weiss et al. (7) showed that calorie restriction led to reductions in muscle mass and aerobic fitness. More recently, Hector et al. (2) confirmed that energy restriction is consistently associated with loss of skeletal muscle in both men and women.

3. Impaired Muscle Protein Synthesis

Even when protein intake is adequate, being in a prolonged energy deficit can blunt your body’s ability to build muscle by suppressing key anabolic pathways such as mTORC1.

One 2016 study demonstrated that calorie restriction impairs muscle protein synthesis in young women, even when consuming recommended levels of dietary protein.(3)

4. Hormonal Disruption

Low energy availability can also interfere with reproductive, thyroid, and adrenal hormones, often causing symptoms like irregular periods, mood changes, poor recovery, and fatigue.

A study carried out in 2007 explored this extensively, showing that female athletes and active women experiencing chronic energy deficiency were more likely to suffer hormonal disturbances and bone density issues.(4)

How to Support Your Body for Fat Loss and Strength

Eat Enough to Fuel Function

• Avoid eating below your BMR

• If aiming for fat loss, start with a moderate deficit (10–20% below TDEE)

• Reassess frequently — under-eating for too long can halt progress

• Focus on whole foods rather than processed meals

  
  

Prioritise Protein Intake

• Aim for 1.2–2.0g of protein per kg of body weight per day

• Distribute intake across meals to support muscle repair and satiety

  
  

Strength Train Consistently

• Incorporate resistance training 2–4 times per week

• Focus on progressive overload and form

  
  

Track Health Markers, Not Just Weight

• Monitor energy levels, sleep, menstrual health, mood, and physical recovery

• Look for positive signs like better digestion, strong nails, improved libido, and mental clarity

  
  

Final Thoughts

Eating too little is not a sustainable solution — it’s a setup for metabolic resistance, hormonal imbalance, and physical depletion. Supporting your body with the right amount of fuel is the most powerful thing you can do for fat loss, muscle gain, and long-term health.

You deserve to feel strong, energised, and fully nourished — not run-down and restricted.

If you are looking for help with managing your weight look no further. If you're ready to ditch the confusion and get a clear, evidence-based plan tailored to your goals, I’m here to help! With expert nutrition advice and personal training, you’ll get the guidance, support, and accountability you need to achieve real, lasting results.

Book your FREE discovery call today and take the first step towards a healthier, stronger you!

Disclaimer

The information on this blog is here to help and inspire, but it’s not meant to replace professional advice. Always check with a doctor before making any changes to your diet or lifestyle. The views shared are those of the author(s) and may not reflect those of any organisations involved. Rosy Nutrition & Personal Training can’t be held responsible for any outcomes from using this information.

References

1. Nutrium. Mifflin-St. Jeor for nutrition professionals. [online] Available at: https://nutrium.com/blog/mifflin-st-jeor-for-nutrition-professionals/ [Accessed 6th January 2025].

2. Hector, A. J., McGlory, C., Damas, F., Mazara, N., Baker, S. K., & Phillips, S. M. (2017). Pronounced energy restriction with elevated protein intake results in no change in proteolysis and reductions in skeletal muscle protein synthesis that are mitigated by resistance exercise. The FASED Journal. [online] Available at: https://www.researchgate.net/publication/319676421 [Accessed 22nd April 2025].

3. Lee M. Margolis, Donato A. Rivas, Maria Berrone, Yassine Ezzyat, Andrew J. Young, James P. McClung, Roger A. Fielding, Stefan M. Pasiakos. (2016) Prolonged Calorie Restriction Downregulates Skeletal Muscle mTORC1 Signaling Independent of Dietary Protein Intake and Associated micro RNA Expression. Frontiers in Physiology. [online] Available at: https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2016.00445/full [Accessed 22nd April 2025].

4. Loucks, A. B. (2007). Low energy availability in the marathon and other endurance sports: metabolic and hormonal consequences. Sports Medicine, 37(4–5), 387–390. [online] Available at: https://pubmed.ncbi.nlm.nih.gov/17465605/ [Accessed 22nd April 2025].

5. Martin, C. K., Das, S. K., Lindblad, L., Racette, S. B., McCarron, R., & Kraus, W. E. et al. (2007). Effect of calorie restriction on resting metabolic rate and spontaneous physical activity. Obesity (Silver Spring), 15(12), 2964–2973. [online] Available at: https://onlinelibrary.wiley.com/doi/10.1038/oby.2007.354 [Accessed 22nd April 2025].

6. Redman, L. M., & Ravussin, E. (2011). Caloric restriction in humans: impact on physiological, psychological, and behavioral outcomes. Antioxidants & Redox Signaling, 14(2), 275–287. [online] Available at: https://www.liebertpub.com/doi/10.1089/ars.2010.3253 [Accessed 22nd April 2025].

7. Weiss, E. P., Racette, S. B., Villareal, D. T., Fontana, L., Steger-May, K., Schechtman, K. B., & Holloszy, J. O. (2007). Improvements in glucose tolerance and insulin action induced by increasing energy expenditure or decreasing energy intake: a randomized controlled trial. [online] Available at: https://pubmed.ncbi.nlm.nih.gov/17093155/ [Accessed 22nd April 2025].

8. Martin, C. K., Heilbronn, L. K., de Jonge, L., DeLany, J. P., Volaufova, J., Anton, S. D., Redman, L. M., Smith, S. R., & Ravussin, E. (2007). Effect of calorie restriction on resting metabolic rate and spontaneous physical activity. Obesity, 15(12), 2964–2973. [online] Available at: https://doi.org/10.1038/oby.2007.354 [Accessed 22nd April 2025].