If you, like me, find the general advice offered by NHS websites to be largely vague, generic, unhelpful, ineffective or all of these, you can find more in depth and expert advice on this subject from Holford range of books. Specifically, this article is a good place to start.
If you have symptoms like unexpected fatigue, lack of satisfaction from eating meals, feeling hungry after eating, craving sugars and fast foods, stomach discomfort relieved after the loo. I would also include weight gain as a commonly experienced issue.
Ultimately, as Holford suggests, the gut is the second brain and often the gut exerts control over the brain. Such that any discomfort from the gut and the brain is taken over. This means that daily tasks become difficult to focus on, because the gut is demanding all of the brain's attention!
When you read what he has to say, Holford reveals where we are aggravating our gut, and, most importantly, he offers a solution!
For more energy, less pain, more satisfaction from food, and more of your brain available for the important tasks of the day, sort out your gut first.
Start with a large glass of water, perhaps while you read the link above (here it is again)