Weight Loss: Fasting vs Dieting

Calorie restriction (CR) has long been known to have the ability to extend people’s lifespans and help delay some age-associated diseases. Now scientists may have linked fasting to be an integral part of the process to achieving the many health benefits associated with calorie restriction.

This breakthrough in knowledge can be traced back to a study conducted by scientists at the University of Wisconsin. The study was performed on rodents and sought to understand the best approach for fat loss and longevity. They were trying to see which one was more effective in fat loss: restricting calories or fasting, or both.

The Experiment: Fasting Or Calorie-Restricting

To uncover the answer, scientists randomized the animals into four separate groups based on four distinctive feeding patterns:

• Group 1 – Unrestricted access to food (no calorie restriction at all)-
• Group 2 – Free to access a 30% calorie-restricted diet (no feeding window compression)
• Group 3 – Food was only released at three separate time intervals in relation to the mice’s 12-hour feeding period and comprised of a 30% calorie-restricted diet.
• Group 4 – Mice were fed a 30% calorie-restricted diet once per day in the morning causing an extended fast period to occur. This is essentially an OMAD (a type of intermittent fasting) with CR.

The Physiological Impact

As could be anticipated, any mice who were fed with CR implemented had lower levels of their energy expenditure. Mice in groups 3 and 4 showed improvements in their body composition, ability to tolerate glucose, and sensitivity to insulin sensitivity; thus, suggesting that prolonged fasting is essential in accomplishing these effects.

Next, researchers looked at the relationship between additional fasting with CR and fatty acid oxidation. To do this, the scientists utilized a metabolic chamber to determine what the mice’s respiratory quotient was. The results were clear: mice in groups 3 and 4 demonstrated nearly identical patterns of increased fuel switching during the fasting period, while the ad libitum fed mice showed no increase in fatty acid oxidation.

Moreover, it was discovered that 2,700 genes in the liver and 1,800 genes in fat tissue had different ways they were expressed between mice in groups 3 and 4 compared to the ad libitum control mice. This was a result of the higher levels of fat loss in the animals subjected to compressed feeding windows as more metabolic pathways were changed in white fat tissue than liver.

Scientists also found that six crucial metabolic pathways were enhanced in both tissues of the mice that were fed in compressed feeding windows with CR. The pathways include biosynthesis pathways, insulin signaling, PPAR signaling, fatty acid metabolism, and circadian rhythm. The mice in the third feeding group also saw two important pathways being unregulated in their fat and liver: TGF-beta signaling pathway and longevity-regulating pathway.

Finally, the researchers assessed how each feeding pattern impacted lifespan. It was shown that the mice in group 4 had a longer lifespan of about 1,022 days, or nearly 3 years. That’s about a one-fifth longer than the 850-day lifespan of the ad lib-fed mice. These mice also showed less frailty, a more enriched abdomen, and better preservation of fur and coat color across a 24-month period versus the mice in group 1.

What’d They Find Out

The study’s results suggest that fasting is a necessary component for calorie restriction to enhance insulin sensitivity and create the metabolic switch to increase fatty acid oxidation. This is how fat mass is reduced. Fasting also appears to reduce age-related frailty and the potential diseases that old age can evoke.

However, one finding shows that having a calorie restriction with no feeding window compression could improve glucose tolerance and positive improvements in body composition.

The takeaway is that there isn’t necessarily one or the other that’s better. But if you are someone looking to improve your metabolic systems and longevity through calorie restriction, understand that the health benefits you are looking for have some overlap with intermittent fasting. Furthermore, you can better achieve these benefits by fasting or eating with CR in a compressed feeding window. Fasting combined with restricting your calories may help you achieve these benefits more quickly.