It’s time to give an old-time and somewhat humorous saying the health and fitness heave-ho. Stop smiling when you hear “The way to a man’s heart is through his stomach.”

Start saying, “The way to improve a man’s health is by feeding the good gut bacteria in his stomach.”

Every time your body digests carbohydrates and proteins, the bacteria in your gut consume some. It’s a significant amount because the number of gut bacteria inside you is staggering.

Add up the good ones and the bad ones and most estimates, including the one given by the European Society of Neurogastroenterology & Motility, are around 100 trillion.

While it’s hard to comprehend any 15-digit number, it’s easy to understand the three-digit one on your bathroom scale. So all you really need to know about the big number is proper attention to it reduces the little one.

Something else easy to understand is that the reduction of the little number usually requires a severe restriction or even an elimination of added sugars in your diet. Do this and chances are you’ll crave sweetness and use one of the many sugar substitutes.

The craving is not because you’re weak-willed or the diet’s a flop. It’s the way we are all hardwired.

Which makes another type of hardwiring - that of those 100 trillion gut microbiota, both good and bad alike - an important consideration. We know the good benefit from a dearth of sugar and a wealth of fiber - and the bad thrive in an opposite situation - but how do both respond to sugar substitutes?

Regular readers know I use two sugar substitutes, stevia and erythritol, extensively, feel both work for me, but that I’m a firm believer in the need to personalize your diet. That there’s no guarantee what works for me will work for you.

One thing I will guarantee, though: Weight loss and the subsequent maintenance of it is essentially a game - and gut bacteria and sugar substitutes are major players. To make you more aware of this game’s rules, let’s call upon two referees from Pendulum Therapeutics, a biotechnology company creating products to improve health by targeting the microbiome: Jennifer McManus, RD, LDN, CDCES and Kristin Neusel, MS, RD, LD, CDCES.

Fitness Master: It’s easy to forget what’s most important about significantly reducing - or some would argue eliminating - the consumption of added sugars because so much has been written about their adverse effects. In your mind, what are the best reasons cut back or even go cold turkey?

Jennifer McManus: The average American’s diet is notoriously high in added sugar and fat, which continues to lead to the rise of obesity, metabolic disease, dysbiosis in your gut, and overall poor health. Added sugar is one of the main contributors to inflammation in the body. Being more mindful and making “healthy swaps” to some of your favorite recipes during the holidays are two ways to keep your sugar intake in check.

It is also so much easier to be able to identify foods that contain added sugars with this feature now being added to the Nutrition Facts label.

FM: In the last 20 years or so, science has found a number of links between the gut microbiome and overall health, yet Harvard Health Publications still calls that environment “as vast and as mysterious as the Milky Way.” At this point, what can be said about the link for sure?

JM: We know for certain that your microbiome is starting to develop at birth. The delivery method (vaginally or caesarean) and the feeding method (breast fed or bottle fed) have been shown to shape the infant gut microbiome. We also know that the microbiome changes over time with many controllable and uncontrollable factors, including the aging process, changes in environment, diet, medications, stress, and progression of different diseases.

It is important to point out that one controllable factor in the link between the gut microbiome and overall health is diet. The standard American diet is typically very low in dietary fiber, and soluble fiber is the main source of food for the good bugs inside of the gut.

FM: Similarly, many find the choice of sugar substitutes and the question of their safety to be vast and mysterious. Generally speaking, where do you stand on their use?

Kristin Neusel: Great question! Sugar substitutes include aspartame, stevia, saccharin, sucralose, and monk fruit. The potential downside to sugar substitutes is that they could impact the gut microbiome in a not-so-sweet way.

Studies have shown that consumption of different sugar substitutes decreased the abundance of some of the beneficial bacteria in the gut.

FM: Specifically speaking, are there any that are particularly good for the gut microbiome?

JM: If I had to pick a sugar substitute to recommend, I would opt for stevia as it is plant-derived. The roots of stevia actually contain inulin and fructans, which can be food for specific strains of the gut microbiome.

FM: Any that are particularly bad?

KN: There is a lot of concern surrounding the impact of sugar substitutes on the gut microbiome. However, the issue is there is just not enough clinical evidence to come to a complete conclusion on which ones, if any at all, are “bad.”

Further studies definitely need to have a more firm understanding of the shifts these sugar substitutes have on the gut microbiome.

FM: Could you specifically address how a few affect overall health?

JM: People are attracted to sugar substitutes because they contain zero calories. This is helpful for someone who is seeking weight loss as these sugar substitutes help reduce their overall calorie intake.

However, the long-term effect of weight loss with the intake of sugar substitutes remains unclear. Sugar substitutes also have a gentler effect on blood sugar levels in comparison to their table sugar (sucrose) counterpart. For individuals with diabetes, consumption of sugar substitutes is a benefit as they generally do not raise blood sugar levels.

With anything, moderation is key when choosing sugar substitutes.

FM: Could you provide a dietary strategy for those who would like to improve their gut health with regards not only to the use of sugar substitutes but also optimal health?

JM: Fiber, fiber, and more fiber! As I briefly noted earlier, fiber is the main source of food for the bacteria inside of our gut.

These “good bugs” need fiber to survive and thrive! Fiber is a carbohydrate, however, it is a type of carbohydrate that passes through the body undigested - meaning it will not impact your blood sugar levels. Soluble fiber, specifically, feeds the gut microbiome.

Eating more soluble fiber helps keep the microbes in your gut happy, healthy, and diverse, which leads to overall improvements in your gut health. The top fiber-containing foods are whole fruits, vegetables, nuts, seeds, whole grains, beans, peas, and other legumes.

The crowd-favorite, fiber-containing foods include avocados, chickpeas, blackberries, raspberries, lentils, chia seeds, and almonds. These foods are easy to snack on, but are also an easy addition to any meal, soup, or salad.