Does Malnutrition Always Affect Thinking in Anorexia?

What a 2024 study shows — and what it doesn’t

The study in brief

Paper: Cognitive Functions in Adolescent Girls with Anorexia Nervosa during Nutritional RehabilitationJournal: Nutrients (2024)

Participants: 36 hospitalised adolescent girls with anorexia nervosa, compared with 48 healthy peers

Design: Cognitive testing during acute malnutrition and again after partial nutritional rehabilitation

The study explored whether severe malnutrition in anorexia nervosa impairs cognition, and whether cognitive function improves with weight restoration.

What the researchers expected

Based on existing knowledge, the authors expected that:

• Severe malnutrition would impair cognitive function

• Cognition would improve with nutritional rehabilitation

• Blood markers (e.g. anaemia, thyroid changes) would reflect severity

These assumptions mirror how eating disorders are often conceptualised clinically.

What they actually found (and why this is often misunderstood)

1. Cognitive performance was not reduced during acute malnutrition

Unexpectedly:

• Adolescents with anorexia performed as well as or better than healthy peers across several cognitive domains

• Areas such as attention, planning, spatial perception, and memory were often elevated

• Cognitive performance improved further with nutritional rehabilitation

This has already been misinterpreted as evidence that malnutrition “doesn’t affect the brain.”That conclusion would be incorrect.

2. Cognitive improvement with refeeding was real — but uneven

After nutritional rehabilitation:

• Improvements were seen in memory, processing speed, attention, and coordination

• Some traits (e.g. inhibition, estimation, spatial skills) remained high regardless of weight

• Cognitive flexibility (“shifting”) did not differ significantly at any stage

This suggests that some cognitive traits are not purely state-dependent, particularly in adolescents.

3. Blood tests were largely reassuring

Despite significant malnutrition:

• Most blood markers were within reference ranges

• Thyroid changes were subtle

• Vitamin D was low across all groups

• No laboratory measure reliably reflected cognitive or clinical severity

Clinically, this reinforces a known risk: normal bloods do not equal medical or neurological safety.

What this means clinically (the missing context)

Adolescents can compensate — temporarily

The adolescent brain has a high compensatory capacity. In practice, this can look like:

• Strong academic performance

• Clear reasoning

• Good memory and focus

• Apparent insight and engagement

This compensation is not protection. It is a stress response, not a sign of health.

Anosognosia helps explain the disconnect

Anorexia nervosa is commonly associated with anosognosia — a reduced ability to recognise illness severity.

This means a person can:

• Think clearly

• Argue convincingly

• Appear “high functioning”

…while still being unable to accurately assess risk or need for care.

This study reinforces why self-report, apparent insight, and cognitive performance are unreliable indicators of safety.

The starvation “honeymoon” phase

Clinically, many individuals experience an early honeymoon phase of starvation, characterised by:

• Feeling calm or emotionally blunted

• Increased focus or productivity

• Reduced anxiety

• A sense of control or clarity

Neurobiologically, this likely reflects:

• Stress-hormone–driven arousal

• Dopaminergic reinforcement

• Suppression of hunger cues

• Narrowed emotional range (which can feel like relief)

This phase is:

• Time-limited

• More common earlier in illness

• Lost as malnutrition deepens or illness duration increases

Feeling cognitively or emotionally “better” during starvation is not recovery — it is an illness-driven state that often precedes decline.

This study appears to capture adolescents within that compensatory window.

When food rules feel like being a “good person”

Another key clinical layer is moralisation of eating behaviour.

Many people with anorexia describe:

• Feeling like a “good”, disciplined, or worthy person when following food rules

• Shame or self-contempt when eating flexibly

• A strong identity built around restraint and control

This moral framework is reinforced by diet culture, which equates thinness and restriction with virtue. When restriction feels morally “good,” malnutrition is easily reframed as responsibility or health.

Why parents and carers may miss risk (and why this is not their fault)

Parents and carers are exposed to the same cultural messages:

• Thinness equals health

• Control equals discipline

• Weight loss is often praised

So when a young person:

• Eats “clean”

• Loses weight

• Appears calm, focused, and cognitively sharp

…it may not immediately raise alarm.

This is not parental failure.It reflects societal conditioning that obscures the dangers of starvation.

What this study does not mean

It does not show that:

• Malnutrition is harmless to the brain

• Cognitive testing can rule out severity

• “High-functioning” patients are medically safer

• Normal labs equal recovery

• Adolescents are protected long-term

The authors themselves caution that cognition and blood markers are poor early indicators of illness severity.

What this means for recovery

If someone in recovery is thinking:

• “I can still think clearly, so I must be okay”

• “My blood tests are normal”

• “I feel calmer when I restrict”

• “I’m functioning, so treatment can wait”

This study actually suggests the opposite:

The brain may be compensating — not thriving.

Early intervention matters precisely because this compensatory phase does not last.

Bottom line

This study does not minimise anorexia nervosa. It explains why the illness is so easily underestimated early on.

Preserved cognition, improved mood, moralised restriction, normal labs, and apparent insight can all coexist with significant medical risk.

• For clinicians: don’t be reassured by performance

• For families: trust concern over appearances.

• For individuals: you don’t have to collapse to deserve care.

To learn more about how Malnutrition affects the brain, read here.

ReferenceJowik-Krzemińska K, et al. Cognitive Functions in Adolescent Girls with Anorexia Nervosa during Nutritional Rehabilitation. Nutrients. 2024;16:3435. https://doi.org/10.3390/nu16203435