I have taken out some parts of a long "article" named "guidelines for the nutritional management of anorexia nervosa" you can read if you click the link at the end of the first section. It is worth reading.
A weekly weight gain of 0.5–1.0 kg is generally regarded as optimum. There
is some preliminary research evidence that a minimum weight gain of 0.5 kg per
week results in greater weight gain at discharge than use of a higher minimum
(Herzog et al, 2004). A gain of 1 kg per week requires an energy intake of 1000 kcal
(4200 kJ) daily above the maintenance requirement. An intake of 2200–2500 kcal
(9200–10 500 kJ) daily will promote weight gain of 0.5–1.0 kg per week in most
patients. The rate of gain will slow down as weight increases, owing to an increase
in metabolic rate and physical activity. It may be appropriate to increase energy
intake to compensate for this or to allow a slower rate of weight gain in order to
facilitate stopping at the agreed maintenance figure.
http://www.rcpsych.ac.uk/files/pdfversion/cr130.pdf
For those who eat carbs when refeeding: Hypophosphataemia may develop rapidly during refeeding; if severe, it can
cause cardiac and respiratory failure, delirium and fits. Malnourished patients
are likely to be phosphate-deficient. When refeeding begins, metabolism of
carbohydrate increases and phosphate reserves may be exhausted. Ingestion of
large quantities of carbohydrates, such as occurs during refeeding, may result in
a precipitate drop in serum phosphate levels (Solomon & Kirby, 1990; Fisher et
al, 2000; Winston & Wells, 2002; Hearing, 2004). Adequate amounts of phosphate
should be supplied from the diet. A high phosphate to carbohydrate ratio can be
achieved by including at least 600 ml of milk per day, and avoiding the use of
sugar and high-sugar foods for the first week or so of refeeding. The use of
prophylactic phosphate supplements has been advocated (Fisher et al, 2000) but
has not been subjected to evaluation.
Some patients develop peripheral oedema in the early stages of refeeding. It
appears to be particularly common in those who have misused laxatives or
induced vomiting prior to admission. In severe cases it can lead to rapid weight
gain of several kilograms, but usually begins to resolve in 7–10 days. Refeeding
oedema should be distinguished from cardiac failure, of which other signs are
absent.
Planning the diet should include particular
attention to the following:
• regular, stable intake of carbohydrate, to prevent erratic weight changes;
• adequate intake of protein, especially for vegetarians, those who avoid
dairy products and those with increased protein requirements (e.g. in
infection);
• adequate intake of essential fatty acids;
• adequate intake of nutrients necessary to support bone mineral density
(calcium, vitamin D, magnesium);
• iron and zinc for those who do not eat red meat;
• fat-soluble vitamins;
• the need for long-term, well-balanced vitamin and mineral supplementation;
• the need for supplementation with specific nutrients that are difficult to
provide in adequate amounts from the diet, especially where there are
increased requirements.
Managing hunger should be addressed in planning.
For most people, it is not
possible to abolish hunger while at a low body weight, although some deny it or
appear not to experience it. A number of approaches may help the patient to
manage hunger and prevent overwhelming craving. They include regular,
frequent meals and snacks; eating slowly; including adequate amounts of starchy
carbohydrate and, if possible, some fat in the diet; and constructing meals with a
variety of foods. Some individuals may appreciate including controlled amounts
of foods which they like but find difficult to allow themselves.
Oral feeding requirements
The estimated average energy requirement in the UK for healthy girls aged 11–
18 years ranges from 1845 kcal to 2110 kcal (7750–8860 kJ) per day; for boys of the
same age the range is 2220 kcal to 2755 kcal (9325–11 570 kJ) per day (Department
of Health, 1991). As with adults, children and adolescents with anorexia require
hypercaloric diets in order to gain weight, especially when approaching a
minimum healthy level.
Most authorities suggest that teenage girls who are
anorexic require an energy intake in excess of 3000 kcal (12 600 kJ) daily to
achieve full weight restoration, whereas the American Psychiatric Association
(Anonymous, 2000) recommends 70–100 kcal/kg (295–420 kJ/kg) per day. Energy
needs are obviously greater in young, growing adolescents and it often becomes
difficult for those with anorexia to ingest enough energy to gain weight.
Increased energy needs continue into the maintenance period. Kaye et al (1986)
have shown that people with anorexia require an extra 200–400 kcal (840–1680 kJ)
a day for up to 6 months after reaching maintenance weight. Weltzin et al (1991)
reported that recovering patients required 45–50 kcal/kg (190–210 kJ/kg) per
day to maintain 95% average weight for height, compared with 30 kcal/kg (125
kJ/kg) per day in a healthy control group. The American Psychiatric Association
(Anonymous, 2000) suggests using 40–60 kcal/kg (170–250 kJ/kg) per day during
the weight maintenance period. It has also been demonstrated that people with
restricting anorexia require significantly more energy than those with the binge/
purging subtype (Kaye et al, 1986; Weltzin et al, 1991).
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