What are the initial steps to manage low energy in a 25-year-old female?

Initial Management of Low Energy in a 25-Year-Old Female

Begin by systematically screening for low energy availability (LEA) and relative energy deficiency, as this is the most common and treatable cause of fatigue in young women, affecting up to 47% of physically active females in this age group. 1

Step 1: Immediate Assessment

Conduct a targeted history focusing on:

• Menstrual history: Ask specifically when her last menstrual period occurred, how many periods in the past 12 months, cycle regularity (normal is 21-35 days), and any hormonal contraceptive use 1
• Weight and eating patterns: Recent weight changes, intentional dieting, food restriction patterns, concerns about weight, and whether she avoids certain food groups 1
• Exercise habits: Type, frequency, duration, and intensity of physical activity, including whether she participates in weight-sensitive sports or activities 1
• Energy-related symptoms: Recurrent injuries (especially stress fractures), frequent illnesses, gastrointestinal issues, decreased performance, mood changes, or concentration problems 1

Step 2: Calculate Energy Status

Assess for low energy availability, defined as energy intake minus exercise energy expenditure relative to fat-free mass <30-45 kcal/kg FFM/day. 1

Key clinical indicators without formal calculation:

• BMI <18.5 kg/m² or <85% expected body weight suggests overt low EA 1
• Weight stability does NOT rule out low EA, as metabolic adaptation can restore energy balance at suppressed physiological function 1
• Recent unintentional weight loss of any amount warrants concern 1

Step 3: Determine the Pathway to Low Energy

Identify which of four distinct pathways led to low EA, as this determines the treatment team required: 1

1. Inadvertent undereating (no eating disorder): Refer to sports dietitian for nutritional education 1
2. Disordered eating without clinical eating disorder: Refer to physician AND sports dietitian 1
3. Intentional weight loss without disordered eating: Refer to sports dietitian for nutritional education 1
4. Clinical eating disorder (anorexia, bulimia, binge eating): Requires physician, sports dietitian, AND mental health practitioner—psychological treatment is mandatory as nutritional intervention alone will fail 1

Screen for eating disorder risk using questions about: dieting behaviors (51% of at-risk athletes diet), body image concerns, binge eating, purging, laxative use, or excessive exercise specifically for weight control 2

Step 4: Initial Laboratory Evaluation

Order baseline tests to assess physiological consequences:

• Complete blood count (assess for anemia) 3
• Comprehensive metabolic panel (potassium monitoring is critical in first 48 hours of refeeding) 3
• Thyroid function (TSH, free T3—low T3 indicates metabolic suppression from LEA) 1, 4
• Iron studies and vitamin B12 (deficiency causes fatigue and requires lifelong replacement if pernicious anemia) 3
• Consider bone mineral density via DXA if menstrual dysfunction >6 months or history of stress fractures 1

Step 5: Implement Nutritional Intervention

The primary treatment goal is restoring energy status through increased energy intake and/or decreased exercise energy expenditure. 1

Specific targets:

• Increase caloric intake by 300-600 kcal/day (20-30% above baseline) to achieve weight gain of approximately 0.5 kg every 7-10 days 1
• Minimum energy intake should be at least 2000 kcal/day, adjusted upward based on exercise expenditure 1
• Target energy availability ≥45 kcal/kg FFM/day 1
• For underweight athletes with amenorrhea, expect 5-10% body weight gain (1-4 kg) to restore menses 1

Recovery timeline varies by system: Energy status improves within days to weeks; menstrual function returns after months; bone mineral density may require years to normalize 1

Step 6: Modify Exercise if Necessary

Consider reducing training volume by introducing rest days or decreasing exercise intensity, particularly if the patient is unwilling or unable to increase energy intake sufficiently 1

Critical Pitfalls to Avoid

• Do not prescribe oral contraceptives to "treat" amenorrhea—this masks the underlying energy deficiency without correcting it and may compromise peak bone density attainment 1
• Do not give folic acid >0.1 mg/day without ensuring B12 adequacy—this can mask B12 deficiency while allowing irreversible neurologic damage to progress 3
• Do not assume weight stability means adequate energy—metabolic adaptation can maintain weight despite ongoing physiological suppression 1
• Do not delay psychological referral if eating disorder is suspected—nutritional intervention will fail without concurrent mental health treatment 1

Non-Athletic Considerations

If the patient is not physically active, expand differential to include:

• Vitamin B12 deficiency (requires 100 mcg IM daily for 6-7 days if deficient, then monthly for life) 3
• Iron deficiency anemia 3
• Thyroid dysfunction 4
• Depression or other psychological conditions 1, 4

Monitor response closely: Reticulocyte count should increase by days 5-7 of treatment; if not, reassess diagnosis and consider complicating factors 3