All sorts of factors will affect the composition and function of our microbiota, and therefore our gut health, including:

What is a healthy gut?

There is actually no specific definition of what makes a healthy gut, because that depends so much on the individual. But in general, I would consider a healthy gut to:

1. Be free from persistent digestive symptoms (such as bloating, abdominal pain or disrupted bowel habits). We all get the odd symptom from time to time though, which is absolutely normal.
2. Eliminate regular, formed (but easily passed) stools.
3. Allow complete digestion and absorption of nutrition. The average time for the entire process of digestion / absorption is 24 hours, although this does vary a lot between individuals.

What is an unhealthy gut?

There are certain unhealthy gut symptoms which are known as ‘red flags’. These are important warning signs that should be discussed with a doctor as soon as possible. Although some of them may represent a harmless condition that will settle itself, it is important if you have any of these symptoms to seek a medical opinion promptly:

• A sudden, persistent change your bowel habits
• Any bleeding, or black, tarry stools
• Increasing heartburn, indigestion or stomach pains
• Losing weight unintentionally
• Any difficulty or pain on swallowing

Within the scope of my nutritional practice, I would also look at all sorts of other symptoms (even if they are not necessarily directly related to the gut), such as skin, mood, energy, weight and much more.

How might gut health affect weight?

We know that our gut needs to function effectively to be able to digest and absorb the nutrition that we are eating. This can lead to both underweight and overweight. Perhaps the most important question to ask is firstly whether there could be an underlying medical problem that is driving poor digestion? The best way to work out if this is a possibility is to speak to your doctor or other healthcare provider. These problems usually lead to an unintended decrease in weight (although not always).

Once this has been ruled out, the next step would be a more comprehensive look at overall digestion, and whether there are any signs and symptoms of maldigestion, gut inflammation or irritation. This is often highly variable between people, so I would suggest that you find a well-qualified Nutritional Therapist or Registered Nutritionist (see FAQs for more info) –  ideally with some training on Functional Medicine –  to help you, if necessary. I run stool, blood, urine and saliva tests where necessary in my practice to help identify what might be going on for each individual.

There is also a lot of interest in the science world at the moment around the potential role of the gut microbiota in the development of obesity, and obesity-related diseases. Lots of this revolves around how certain microbes alter energy absorption by the body. In simple terms, the composition of our microbiota can cause us to either absorb less, or more, energy from exactly the same plate of food.

I think about it in terms of ‘energy harvesting’ – some microbes help us to do this more efficiently than others. One of the ways that our microbes do this is by producing specialized enzymes that help to break down carbohydrates and proteins that would normally be indigestible (Krajmalnik-Brown et al., 2012). The more energy we harvest, the more we absorb.

Unfortunately, we do not know enough about this topic yet to know which types of microbe would help us to lose weight (or indeed, help us to gain weight). However, there are some promising studies emerging (Kadooka et al., 2010).

watch this space!

Head over to Part 2: Probiotics and Prebiotics in gut health. In Part 3: How to nourish your gut, we shall explore how to nourish your gut health, with lots of ideas on how to do this.