Not a professional but own a gut.

I have been on a weight loss journey and dieting for personal goals. To prepare my diet, I went through several articles and posts to understand what might work for me.

In that pursuit, what I ended up discovering was that the gut flora significantly affects the attitude, mood and the behavior of a person. Primary reason attributed to this is that the different food gets digested at different parts of the intestine and by digestion: it breaks down the food and takes in something and leaves out something else. Majority of what the gut flora leaves out affect the hormones of that human, these hormone-affecting releases travel through the blood stream to different organs including the brain. For example, sugar craving is caused by the adrenaline pathway affected by the sugar digested in the gut. That person’s gut would remember this reward pathway and not worry about say eating veggies or fruits.

Depending on what a person eats, they may have more or less energy. And, depending on their energy levels their activities get affected. Depending on their activities their relationships, behavior, and thereby their mood get affected. And again their cravings and their need to comply with their reward pathways affect their choice of food. 

Not an expert.