Longevity Briefs: A Diet That Boosts Gut Health And Weight Loss With A Twist

Longevity briefs provides a short summary of novel research in biology, medicine, or biotechnology that caught the attention of our researchers in Oxford, due to its potential to improve our health, wellbeing, and longevity.

The problem:

Extending an organism’s lifespan is actually surprisingly easy. In many animals, simple calorie restriction (sharply cutting calorie intake without causing malnutrition) is enough to extend maximum lifespan significantly beyond what is expected of their species. There are many different ways of restricting calories. Limiting daily intake is the most straightforward and the most studied, but is also very hard for humans to maintain over a long period of time. For this reason, many turn to intermittent forms of calorie restriction, such as fasting on alternate days or restricting feeding to a narrow time window each day.

In today’s study published in Nature, researchers looked at one such method that they call periodic restricted feeding. Studying its effects in macaque monkeys – one of our most closely related animal relatives – they revealed some interesting outcomes for metabolic and gut health.

The discovery:

In the study, 23 monkeys were divided into a control group or a periodic restricted feeding group. The restricted feeding group had their calorie intake restricted for four days. Calories were cut by 50% on the first day and by 70% on subsequent days. After that, the monkeys were allowed to eat as much as they wanted for ten days. This pattern was repeated six times. The control group, meanwhile, had unrestricted access to food.

Unsurprisingly, the calorie restricted monkeys lost weight compared to the controls. On average, they lost 5% of their starting body mass. Interestingly, when the experiment ended, only the male monkeys maintained their weight loss during the three-year follow up period, while the female monkeys quickly regained their lost weight. This seemed to be related to differences in metabolism – during restricted feeding, the monkeys underwent various metabolic adaptations, mainly an increased use of lipids (fat) for energy. When the experiment ended, these metabolic changes returned to baseline in males, while females ‘overcorrected’.

Researchers then analysed the microorganisms living in the monkeys’ guts. They found that after three cycles of restricted feeding, the monkeys benefited from increased α-diversity, a measurement of the number and diversity of different gut bacteria. They also found beneficial changes in types of bacteria that have been linked to health in humans. For example, restricted feeding was associated with increased levels of Verrucomicrobia, which has been linked to protection from obesity, while levels of Firmicutes – a bacteria linked to diabetes – were reduced.

The researchers didn’t observe any negative side effects from the restricted feeding. In particular, they didn’t measure any significant weakening of the monkeys’ immune system function, which is a common issue with calorie restricted diets.

The implications:

The study presents some evidence, though admittedly not human evidence, that this kind of cyclical calorie restriction might be beneficial for weight loss and gut health. This is no different from other forms of calorie restriction, but does this method offer any advantages? It’s impossible to say until human studies are done, and even then comparing different calorie restriction strategies is quite hard. Any type of calorie restricted diet is likely to be a lot healthier than inaction, so the best diet may simply be the diet that is easiest to adhere to.