Feb. 22, 2024 — Injectable weight loss medications like Wegovy, Saxenda and Zepbound are getting all the glory lately, but they’re not for everyone. If you want to lose a few pounds or avoid obesity, research suggests there’s another way. It may not produce as dramatic results as regular injections, but you can get everything you need at the grocery store for a lot less money — and this approach has the potential to improve your health in countless ways.
In theory, all you need to do is give your gut microbiome a boost.
“There are many different factors naturally involved in weight gain and weight loss, so the gut microbiome is certainly not the only one,” says Chris Damman, MD, a gastroenterologist at the University of Washington. He investigates how nutrition and the microbiome influence your health. “With that caveat, it probably plays an important role.”
Trillions of microbes
The idea that your gut is home to a huge range of tiny organisms – microbes – has been around for more than 100 years, but it’s only in the 21st century that scientists have had the ability to delve into the details.
We now know that you want a robust range of microbes in your gut, especially in the lower intestines, your colon. They feast on the fiber from the food you eat and convert it into substances your body needs. These substances send signals throughout your entire body.
If you don’t have enough microbes or too many of the wrong types, it affects those signals, which can lead to health problems. Over the past two decades, research has linked problems in the gut microbiome to a wide variety of conditions, including inflammatory bowel disease, autoimmune diseases such as rheumatoid arthritis, metabolic diseases such as diabetes, and cardiovascular disease, asthma and even autism.
Thanks to these efforts, we know a lot about the interactions between your gut and the rest of your body, but we don’t know exactly How A lot of things are happening – whether a few little bugs in your microbiome are causing the problems or the other way around.
“That’s the problem with so much of the microbiome stuff,” says Elizabeth Hohmann, MD, a physician-researcher at the Massachusetts General Research Institute. “Olympic athletes have a better gut microbiome than most people. Well, certainly. Because they pay attention to their diet, they get enough rest. Correlation does not lead to causation.”
The American diet messes with your gut
If you’re a typical American, you eat a lot of ultra-processed foods — manufactured with a long ingredient list that contains additives or preservatives. According to one study, these foods make up 73% of our food supply. This can have serious consequences for intestinal health.
“When you process and grind food, the whole food turns into small particles,” says Damman. “That makes the food easily digestible. But if you eat a broccoli stem, a large amount of that broccoli will end up in the form of fiber and other things in your abdomen, where it will feed microbes.”
In contrast, heavily processed foods are digested before they can reach your lower intestines, leaving your microbes without the energy they need to survive.
Rosa Krajmalnik-Brown, PhD, is director of the Biodesign Center for Health Through Microbiomes at Arizona State University. Her lab has been researching how microbes use the undigested food that reaches your intestines. She describes the problem with processed foods this way:
‘Think about a Coke. When you drink it, all the sugar goes into your bloodstream and the microbes in your gut don’t even know you’ve had it. If instead of drinking a cola you eat an apple or something with fiber, some of it goes to you and some of it goes to the microbes. You feed them and give them energy.”
Weight and your gut microbiome
The link between gut health and body weight has received a lot of attention. For example, research has shown that obese people have less diversity in their gut microbiome, and certain specific bacteria have been linked to obesity. Animal studies have shown that transplanting gut microbes from obese mice to ‘germ-free’ mice caused those GF mice to gain weight. This suggests that obesity is in fact caused by certain microbes, but so far there is little evidence that the same is true in humans.
Krajmalnik-Brown’s group did an experiment in which they had people follow two different diets for 23 days each, with a break in between. Both provided similar amounts of calories and macronutrients each day, but through different foods. The study’s typical Western menu consisted of processed foods – think grape juice, sandwiches made with turkey delicacies and white bread, and spaghetti with pot sauce and ground beef. The other menu, what researchers called a “microbiome booster diet,” included foods such as whole fruit, vegetarian sandwiches on multigrain rolls, and steak with whole-wheat spaghetti.
Although the study wasn’t aimed at weight loss, something interesting happened when researchers analyzed participants’ bowel movements.
“We found that when you give subjects a diet that is designed to give more energy to the microbes and not to the microbes [body], our subjects lost a little bit of weight,” Krajmalnik-Brown said. “It appears that feeding your microbes makes people healthier and possibly even lose a little weight.”
Another possible mechanism is the same hormone that powers the injectable weight loss drugs. The lower part of your intestines produces hormones that tell the entire intestine to slow down and also help orchestrate metabolism and appetite. Among them is GLP-1. The drugs use a synthetic version, semaglutide or tirzepatide, to produce the same effect.
According to Damman, you can stimulate your gut to produce those beneficial hormones with the food you eat by giving your microbes the right fuel.
Eat to feed your microbes
The food you eat can affect your gut microbiome, and therefore your weight. But don’t look for that one perfect ingredient, experts warn.
“A lot of times we get this micro-focus: Is this good food or bad food?” warned Katie Chapmon, a registered dietitian whose practice focuses on gut health. “You just want to make sure that your microbiome is robust and healthy so that it communicates that your body is active and that you have it.”
Instead, try giving your body more of these things food research has shown that they can nourish your microbiome, many of which are plant-based. “Those are the things that are largely removed during processing,” says Damman. He calls them the “Four F’s”:
- Fiber: When you eat fiber-rich foods such as fruits, vegetables, whole grains, nuts and beans, your body cannot digest the fiber while it is in the upper parts of your gastrointestinal tract. It continues to your lower intestines, where healthy bacteria ferment it. That produces short-chain fatty acids, which send signals throughout the body, including signals related to appetite and feeling full.
- Phenols: Phenolic compounds are antioxidants that give plant foods their color. When you talk about eating the rainbow, you’re talking about phenols. The microbes in your intestines also feed on it. “My goal for a meal is five different colors on the plate,” Chapmon said. “That rounds out the bases for the different polyphenols.”
- Fermented Foods: You can get a different kind of health benefit by eating foods that have already been fermented, such as sauerkraut, kimchi, kefir, yogurt, miso, tempeh, and kombucha. Fermentation can make the phenols in foods more accessible to your body. Plus, every bite introduces good bacteria to your body, some of which end up in your intestines. The bacteria already there feed on these new strains, helping to increase the diversity of your microbiome.
- Healthy fats: This isn’t so much about feeding the good bacteria in your microbiome. Damman says omega-3 fatty acids, found in oily fish, canola oil, some nuts and other foods, reduce inflammation in the lining of your intestines. Plus, healthy fat sources like extra virgin olive oil and avocados are full of phenols.
Eating for gut health is not a panacea when it comes to weight loss. But the benefits of a healthy gut go far beyond losing a few pounds.
“I think we should aim for health, not weight loss.” said Krajmalnik-Brown. “Keep your gut healthy and your microbes healthy, and that should ultimately lead to a healthy weight. You will make your microbes happy, and your microbes will do a lot for your health.”