The Trap of Undereating

We are all aware that to lose weight, we must be in a calorie deficit. That is, we have to consume less than we burn. So, it stands to reason that the less we eat, the faster we should lose weight. But this isn’t the case, especially if the goal is to lose fat but keep the toned muscle we’ve been building so diligently at the gym.

If you eat less than you burn, you will lose weight, but you may not like how you look. Think of the “skinny fat” person who barely makes the dial on the scale budge, but whose arms and legs look like sticks (or worse, flabby sticks!)

Is that the look you want? Or would you rather look fit, toned, and have the energy to get through the day without feeling exhausted and crabby?

The truth is, if you’re in a calorie deficit, you are bound to be a little bit hungry. That’s how you know you’re in a deficit! But there’s a fine line between a healthy deficit and one that defeats the goal you’re trying to reach.

Undereating is a trap. Here’s why:

Initial fat loss may occur, but prolonged severe calorie restriction backfires:

• You lose muscle tissue as your body breaks it down for energy.
• Your metabolism slows down to conserve energy (known as adaptive thermogenesis).
• You may experience fatigue, brain fog, mood swings, and poor recovery from workout.

Why Lean Muscle Matters During Fat Loss:

• Muscle is metabolically active, meaning it helps you burn more calories at rest.
• Maintaining muscle:
  • Keeps your metabolism higher. Improves your shape and strength
  • Enhances your fat loss results (since a higher % of weight lost is fat, not muscle).

Signs You’re Undereating:

• Constant hunger or binge eating episodes
• Plateauing or gaining weight despite “dieting”
• Loss of strength or performance
• Poor sleep or hormonal changes (irregular periods, low libido)
• Cold sensitivity or low energy

Ideal Approach for Fat Loss with Muscle Maintenance:

1. Moderate Calorie Deficit: Aim for a 15-25% deficit from your maintenance calories.
2. High Protein Intake: 0.8 – 1.2 grams per pound of bodyweight.
3. Strength Training: At least 2-4 sessions per week to stimulate muscle retention.
4. Adequate Recovery: Sleep, stress management, and rest days.
5. Smart Cardio: Use as a tool, not a crutch – too much can increase muscle loss risk.

Example:

• Maintenance Calories: 2,500
• Safe Deficit: Around 500 calories
• Target Intake: 2,000 (not 1,200 or less)

If you cut to 1,200 – 1,400 calories instead, your body sees that as a stress signal and begins breaking down muscle, holding onto fat, and lowering your metabolic rate. (Your body is smart!)

Bottom Line:

Eating too little sabotages fat loss by increasing muscle loss, slowing metabolism, and harming performance and recovery. Instead, aim for a controlled deficit, high protein, and resistance training to preserve lean mass and optimize long-term fat loss.

References:

Study: Pasiakos, S.M., et al. (2013). Effects of protein supplements on muscle mass and strength in healthy adults: a systematic review. https://doi.org/10.3945/ajcn.112.055061

Study: Dulloo, A.G., et al (1997). Adaptive reduction in basal metabolic rate in response to food deprivations in humans. https://doi.org/10.1152/ajpregu.1997.273.2.R496

Study: Longland, T.M., et al. (2016). Higher protein intake during a hypocaloric diet helps preserve lean mass and promote fat loss in young men.https://doi.org/10.3945/ajcn.115.119339

Study: Phillips, S.M. (2014). A brief review of critical processes in exercise-induced muscular hypertrophy. https://doi.org/10.1016/j.smhs.2014.11.005

Review: Fothergill, E., et al. (2016). Persistent metabolic adaptation 6 years after “The Biggest Loser” competition. https://doi.org/10.1002/oby.21538

Textbook: “Nutrition for Sport and Exercise” (Dunford & Doyle)

Review: Helms, E.R., et al (2014). Evidence-based recommendations for natural bodybuilding contest preparation. https://doi.org/10.1519/JSC.0000000000000362

Position Stand (ISSN): Jager, R., et al. (2017). Protein and exercise: Position stand of the International Society of Sports Nutrition. https://doi-org/10.1186/s12970-017-0177-8