You misunderstand. When it comes to what works for you, an individual, the only thing you can ultimately go on is how you, the individual, feel.

The whole problem is that junk food and overeating feel really good.

They don't the next day. That seems to be more the point.

What is actual science?

Are studies asking people how many times they eat food X per week and correlating on that information science?

The study in the link has a sample size of 14, is that ” actual” science?

Actual science requires the "scientific method" to be followed. Which implies, loosely, that experiments yield repeatable results.

This seems like an uncharitable take: OP seems to be arguing you should focus on what you can measure (even if it’s personal experience), and seek guidance when you need help.

The concrete advice at the end seems pretty supported by science. Drinking and smoking are definitively bad for you.

smoking - yes, it's incontrovertible. drinking - less clear; mortality rates for teetotallers (total abstinence) are higher than for even moderate to heavy drinkers, and there are health benefits from eg 1-2 servings of red wine. IMHO the issue is the degree to which people slip from a drink or maybe 2, to 3 or maybe 4.

Most people that are sick stop drinking. This polluted the early studies on alcohol safety.

More recent studies have pointed in the direction of “no safe quantity of alcohol”.

Thanks. Wish I had a citation handy; I do recall reading a decent one that accounted for that, looking at lifelong habits. (shrug)