options nocenter nodate;
run;

data one;
  input id diet $ wg;
  cards;
4  A 28
3  A 33
1  A 30
9  A 37
11 B 23
7  B 28
8  B 25
10 B 24
2  C 31
12 C 28
6  C 33
5  C 28
;

proc glm;
  class diet;
  model wg=diet / clparm;
  lsmeans diet / cl;
  estimate 'Diet A Mean' intercept 1 diet 1 0 0;
  estimate 'Diet A Mean - Diet B Mean' diet 1 -1 0;
  estimate 'High Protein vs. Lower Protein' diet .5 -1 .5;
  estimate 'High Protein vs. Lower Protein (2)' diet 1 -2 1 / divisor=2;
  estimate 'High Protein vs. High Protein' diet 1 0 -1;
  contrast 'High Protein vs. Lower Protein' diet .5 -1 .5;
  contrast 'High Protein vs. High Protein' diet 1 0 -1;
run;