Patients at risk for worst outcomes and higher mortality following infection with SARS-CoV-2, namely older adults and polymorbid individuals, should be checked using the MUST criteria or, for hospitalized patients, the NRS-2002 criteria. The identification of at risk or presence of malnutrition should be an early step in general assessment of all patients,  especially including older adults and individuals suffering from chronic and acute disease conditions.

Subjects with malnutrition should undergo diet counseling from an experienced professional. Target is to optimize their nutritional status.
Energy needs: can be assessed by indirect calorimetry (IC) when available
(ensured sterility of the measurement system) or by predictive equations:

1. 27 kcal / kg body weight (b.w.) / d; total energy expenditure for polymorbid patients aged > 65 years^{2, 3}.
2. 30 kcal / kg b.w. / d; total energy expenditure for severely underweight poly-morbid patients; target should be reached cautiously and slowly due to high risk of refeeding syndrom in these patients^{2, 3}.
3. 30 kcal / kg / d as guiding value for older persons, individually adjusted with regards to nutritional status, physical activity^{2, 4}.

Protein needs:

1. 1 g protein /kg/d in older persons;  individually adjusted with regard to
    nutritional status, physical activity level, disease status and tolerance^{2, 4}
2.  ≥ 1 g protein / kg / d in polymorbid medical inpatients; to prevent body weight loss, reduce the risk of complications and hospital readmission and improve functional outcome^{2, 3}.
   Fat and carbohydrates: adapted to energy needs, fat-to-carbohydrate energy ratio 30:70 (no respiratory deficiency) to 50:50 (ventilated patients) percent.

Subjects with malnutrition should ensure supplementation with vitamin A, vitamin D and other micronutrients. As part of the general nutritional approach for viral infections prevention is supplementation and / or adequate provision of vitamins to potentially reduce disease negative impact^{1, 2}.
In general, low levels or intakes of micronutrients such as vitamins A, E, B6 and B12, Zn and Se have been associated with adverse clinical outcomes during  viral infections^{2, 5}. This notion has been confirmed in a recent review from Lei Zhang and Yunhui Liu¹ who proposed that besides vitamins A and D also B vitamins, vitamin C, omega-3 polyunsaturated fatty acids, as well as selenium, zinc and iron should be considered in the assessment of micronutrients in COVID-19 patients^{1, 2}.
ESPEN experts thus suggest to ensure the provision of daily allowances for vitamins and trace elements to malnourished patients at risk for or with COVID-19, aimed at maximizing general anti-infection nutritional defense.

Patients in quarantine should continue regular physical activity while taking precautions.
Prolonged home stay may lead to increased sedentary behaviors, such as spending excessive amounts of time sitting, reclining, or lying down for screening activities (playing games, watching television, using mobile devices); reducing regular physical activity and hence lower energy expenditure. Thus quarantine can lead to an increased risk for and potential worsening of chronic health conditions, weight gain, loss of skeletal muscle mass and strength and possibly also loss of immune competence.
There is a strong rationale for continuing physical activity at home to stay healthy and maintain immune system function in the current precarious environment^{2, 6}.
Every day > 30 min or every second day > 1h exercise is recommended to maintain fitness, mental health, muscle mass and thus energy expenditure and body composition.

ONS should be used whenever possible to meet patient‘s needs, when dietary counseling and food fortification are not sufficient to increase dietary intake and reach  nutritional goals. ONS shall provide at least 400 kcal / day including 30 g or more of protein / day and shall be continued for at least one month. Efficacy and expected benefit of ONS shall be assessed once a month.

In patients, whose nutritional requirements cannot be met orally, EN should be administered. Parenteral nutrition (PN) should be considered when EN is not indicated or unsufficient.
EN may be superior to PN, because of a lower risk of infectious and non-infectious complications^{2, 3, 4}.
There are no limitations to the use of enteral or parenteral nutrition based on patient age or diagnosis, in the presence of expectable benefit to improve  nutritional status.

If the energy target is not reached with an oral diet, ONS should be considered first and then EN treatment. If there are limitations for the enteral route it could be advised to prescribe peripheral PN in the population not reaching energy-protein target by oral or enteral nutrition. Overlooking administration of adequate calorie-protein may result in worsening of nutritional status with malnutrition and related complications. Adequate assessment of nutrient intake is recommended with treatment with oral nutrition supplements or with enteral nutrition if oral route is insufficient.

EN should be started through a nasogastric tube; post-pyloric feeding should be performed in patients with gastric intolerance after prokinetic treatment or in patients at high-risk for aspiration.
Energy requirements: Patient energy expenditure (EE) should be determined by using indirect calorimetry when available. If calorimetry is not available, VO2 (oxygen consumption) from pulmonary arterial catheter or VCO2 (carbon dioxide production) derived from the ventilator will give a better evaluation on EE than predictive equations^{2, 7}.
Energy administration: hypocaloric nutrition, not exceeding 70 % of EE should be administered in the early phase of acute illness with increments up to 80 –100 % after day 3. If predictive equations are used to estimate the energy need, hypocaloric nutrition < 70 % estimated needs should be preferred over isocaloric nutrition for the first week of ICU stay.
Protein requirements: During critical illness, 1.3 g / kg protein equivalents per day can be delivered progressively. Obese patients: in the absence of body composition measurements 1.3 g / kg “adjusted body weight” protein equivalents per day is recommended. Adjusted body weight is calculated as ideal body weight + (actual body weight – ideal body weight) * 0.33⁶.

In ICU patients who do not tolerate full dose EN during the first week, initiating parenteral nutrition (PN) should be weighed on a case-by-case basis.
Limitations and precautions: Progression to full nutrition coverage should
be performed cautiously in patients requiring mechanical ventilation and stabilization.

Contraindications: EN should be delayed

• in the presence of uncontrolled shock and unmet hemodynamic and tissue perfusion goals;
• in case of uncontrolled life-threatening hypoxemia, hypercapnia or acidosis.

Precautions during the early stabilization period: low dose EN can be started

• as soon as shock is controlled with fluids and vasopressors OR inotropes, while remaining vigilant for signs of bowel ischemia;
• in patients with stable hypoxemia, and compensated or permissive hypercapnia and acidosis.

General comments:
In stablized patients even in prone position, EN can be started ideally after measurement of IC with a target of 30 % of measured energy expenditure. Increase energy administration progessively. Emergency times: predictive equation recommending 20 kcal / kg / d can be used, energy increased to 50 – 70 % of the predicted energy at d2 to 80 – 100 % at d4.
The protein target of 1.3 g / kg / day should also be reached by day 3 – 5. Gastric tube is preferred but in case of large gastric residual volume (above 500 mL), duodenal tube should be inserted quickly. Enteral omega-3 fatty acids may improve oxygenation but strong evidence is missing.
If intolerance to EN is present, PN should be considered.
Blood glucose: maintained at target levels between 6-8 mmol / l. Monitoring of blood triglycerides and electrolytes including phosphate, potassium and magnesium⁷.

Texture-adapted food can be considered after extubation.
If swallowing is proven unsafe, EN should be administered. In cases with high aspiration risk, postpyloric EN or, if not possible, temporary PN during swallowing training can be performed.
The post-extubation swallowing disorder could be prolonged for up to 21 days mainly in the elderly and after prolonged intubation,^{2, 8, 9} which makes this complication particularly relevant for COVID-19 patients.