This could be over feeding of therapeutic feeds (RUTF) or just a dramatically change of the system , which is damanding more and hence forth the child is eating more than it is supposed to.

We looked at this when developing the CTC (now CMAM) program design. Findings were presented at the April 2008 CTC meeting in Washingtion. In short:

• Weight tended to respond to treatment in OTP and SFP.
• MUAC tended to respond to treatment in OTP and SFP.
• MUAC and weight respond to treatment in similar ways:
  • Both exhibit a dose response relationship:
  • Low intensity treatment (SFP) : Slow response (sometimes no response)
  • High intensity treatment (OTP) : Rapid response (MUAC always responds)

MUAC gains were about 0.30 mm per day (ranging between 0.25 mm to 0.51 mm per day). These gains translate to about 2.1 mm per week (ranging between 1.77 mm to 3.57 mm per day) ... quite close to what you have above. At these rates of MUAC gain we'd expect to see a child with MUAC = 110 mm reach 125 mm in about

(125 - 110) / 0.30 = 50 days (range 30 to 43) days

and reaching 120 mm in about:

(120 - 110) / 0.30 == 33 (range 20 to 40) days.

We saw median lengths of stay in programs range between 42 and 50 days.

These results are based on  OTP and SFP research and program data from Ethiopia, Zambia, Malawi, and Bangladesh. Admission MUACs ranged between 102 and 107 mm without oedema (the admission criteria was MUAC < 110 mm).

These data are for child aged 6 to 59 months. I do not have for PLW but this should be quite easy to find.

We present some of this work (focussing on the relationship between MUAC and weight response) in this article:

Binns, P., Dale, N., Hoq, M., Banda, C. & Myatt, M. Relationship between mid upper arm circumference and weight changes in children aged 6–59 months. Archives of Public Health 1–10 (2015) doi:10.1186/s13690-015-0103-y.

This (quite old) article:

Myatt, M., Khara, T. & Collins, S. A review of methods to detect cases of severely malnourished children in the community for their admission into community-based therapeutic care programs. Food and nutrition bulletin 27, S7-23 (2006).

might also interest you.
  
I hope this is of some use. to someone.

hi

dear sir 

you can look at this information at the link below

https://www.ennonline.net/fex/52/childmuacfoodsupplement

https://www.ennonline.net/fex/63/whzmuacbangladesh

https://www.ennonline.net/fex/50/msfmuacprogramming

Results

After 12 weeks of supplementation, weight gain was 12% from baseline and did not differ between short and long children. The increase in MUAC was 6% after ten to 12 weeks of supplementation and did not differ between groups. Weight-gain velocity from baseline showed a similar development between groups throughout supplementation. MUAC-gain velocity from baseline was also similar between groups from week four. The longer children gained in MUAC more quickly than they did in weight over the first two weeks of the study, compared to the short children.