The most common New Year's resolutions revolve around eating healthy and losing weight. And while many are choosing to go on a classic cleanse to reach their goals, microbiologists say it's just not that easy.

"If you're on a two-week diet, forget about it. If you're on a cleanse, forget about it. If you're on a detox, forget about it," warns microbiologist and best-selling author Jason Tetro.

Many people try to take the fast lane to weight loss, but Tetro says it's just not that easy. Microbes inside our bodies can actually dictate the amount of weight we lose, and it can take more than a short-term diet to get them on our side.

"We've got tens of trillions of bacteria in our intestine," he said, "and [they're] very diverse if you're healthy — somewhere between 500 to 1,000 different species."

The microbes interact with our human cells and affect numerous bodily functions, including digestion, metabolism and mental health, he says.

"If that diversity drops, from 500 to maybe 200, it's called disbiosis. We've learned that the functions of our bodies get hampered and there's some consequences that happen — and one of them happens to be weight gain."

Tetro says the western diet — or what he calls the "sad diet" — that's rich in processed food, simple sugars, saturated fats and lots of meat, actually ends up killing our bacterial diversity, often leading to obesity and depression.

But there's hope.

Upping your diversity

"So the idea then is maybe if we increase diversity, we might be able to lose weight — that's the whole concept of dieting."

But Tetro says the increase takes time and can't be done through a simple cleanse, detox or short-term diet.

He points to research done at Washington University in St. Louis, where researchers tested how long it took to change the bacterial diversity in mice based on human diets.

Mice that made the switch from the western diet to a healthy diet showed very little change in their bacterial diversity for the first month. In fact, it took nearly 11 weeks before their bodies began to show physical changes.

On the other hand, when mice switched over from a healthy diet to a western diet, they gained weight in just ten days.

Gut Bacteria

Microbes in your body can be diversified by switching to a proper diet. (Nastassia Davis/Flickr)

Switching to the Mediterranean diet

Much like the mice, Tetro says humans have to be in it for the long haul before they begin to reap some of the desired benefits of a proper diet.

"There's really only one good answer: give up the American diet for good. The pops, the things you see on the convenience shelves — all of that stuff is just empty calories."

He says switching over to the Mediterranean diet is the way to go, which includes:

  • High fibre.
  • Higher levels of polyunsaturated fats like nuts and fish oils.
  • A diversity of meats.
  • Fermented sweets including yogurt, honey, and chocolate that's more than 70 per cent dark.

He says if you plan on making the switch, cut down on the red meats at the beginning, before reintroducing them in moderation when you're six weeks in — it will make the microbes 'happy'.

"When you're eating — just like when a pregnant woman eats for two, you're eating for one hundred million."

With files from CBC's North by Northwest


To listen to the full interview, click on the audio labelled: Weight-controlling microbes can be resistant short-term dieting