He lost weight. He also developed an arrhythmia.
The Truth is "In all things moderation.".
That Is almost always the best advice, especially with your diet. Virtually everyone that I have ever known who adopted some weird philosophy that governed what they ate has had problems. There is so much fat and oil in almost everything that it is pretty restrictive if you try to cut out all fats. The same is true of trying to cut out all carbohydrates, and if you cut out all proteins you will eventually die. It is pretty hard get enough proteins in the types you need if you cut out meat, fish and dairy. I have know a lot of unhealthy vegans.
Of course the biggest fad right now is cutting out almost all carbohydrates and I have know a bunch of people who have had a lot of problems from that. Regardless of what people think now about what previous generations in our culture believed was healthy eating, they tended to make better choices than people do now.
I know that it is a sacrilege to those who believe in cutting out carbs, but the much maligned “food pyramid” at least ensured better diversity in peoples’ diets than all the faddish nonsense that people believe these days. If you want to increase your chances of getting sick and dying, there are not a lot of better ways long term than cutting out the nutrients and fuel that your body thrives on.