MATLAB - remove the frequency at zero in FFT
Frequency bin at zero is simply mean value of your signal. Just take a look on definition of DFT, for zero frequency $k$ we get:

$$\left. X[k]=\sum_{n=0}^{N-1}x[n]e^{-i 2\pi  n\cdot k} \right |_{k=0} \Rightarrow X[0]=\sum_{n=0}^{N-1}x[n]e^{-i 2\pi  n\cdot 0} = \sum_{n=0}^{N-1}x[n] $$

So after you calculate the FFT and divide by number of samples, indeed you get the mean value of your signal.
In order to remove that, please apply the following before the FFT calculation:

Lift = Lift - mean(Lift);