Bad results obtained for LS-SVM regression. Any help?

Hello. Although I read many times the tutorial for this LS-SVM toolbox http://www.esat.kuleuven.be/sista/lssvmlab/ , I'm still having very bad results when I use it for regression.

Here is the code I execute:

% Initialisation of the model
model = initlssvm(X,Y,'f',[],[],'RBF_kernel','o');
% Tuning of the model, optimizing the choice of gam and sig2
model = tunelssvm(model,'simplex','crossvalidatelssvm',{10,'mae'});
% Training 
model = trainlssvm(model);
% Prediction of results
Yt=simlssvm(model,Xt)

The results obtained are far different from the initial ones. I really don't understand what I do wrong. Any one help me, please ? Thank you!