Is stochastic process a martingale?

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Is the stochastic process

$$ X(t):=W\left(\int_0^t f(W(s))\mathrm{d}s\right) $$ a martingale? Here, $f(x):\mathbb{R}\rightarrow\mathbb{R}^+$ is a positive function and $W(s)$ is a standard Brownian motion.