I am not an expert on the Montignac diet, but his death prompted some of my friends to comment on my eating habits. This made me have a look at what this diet was all about.
It appears, it was (it is) a high protein, low fat and moderate carb regime. If people on this diet want to avoid being hungry without putting on weight, they are bound to overdo protein. And what kind of protein would that be? Mostly highly processed animal protein loaded with salt, nitrates, benzopyrens and other carcinogens and oxidized fats (even lean meat contains fat and aged cheese is just loaded with oxidized lipids). Montignac advocated against mixing carbs and fats, but did not see any problems with mixing carbs and proteins, hence Maillard reaction was likely quintessential, as it is in tasty French cousine in general.
And much grain fed meat plus olive oil means loads of proinflammatory omega-6.
On a video from March this year, the guy does not look healthy to me. His skin looks too aged for 66. AGE?
And the high protein itself, with mTOR. If the guy did not do any fasting, or at least skipped some meals "warrior style" (he actually recommended 3 meals a day), then perhaps his mTOR was the driver?