Continuous calorie restriction vs. intermittent fasting and protein-pacing

In this study, Arizona State University researchers and their colleagues analyzed data from a clinical trial involving 41 overweight or obese individuals.

Participants were randomly assigned to follow one of two diets for 8 weeks: continuous calorie restriction or intermittent fasting and protein-pacing.

The caloric restriction diet primarily consisted of whole foods, while the intermittent fasting and protein pacing diet combined whole foods and supplement shakes and bars.

Both diets reduced participants’ total fat, carbohydrate, sodium, sugar, and calorie intake by approximately 40% from their baseline levels, resulting in an average 1,000-calorie deficit.

The intermittent fasting plus protein pacing diet involved 5–6 days of 4 daily meals for women, and 5 meals a day for men, spaced 4 hours apart, each containing 25–50 grams of protein. It also included a 36–60-hour weekly modified fasting period with 350–550 calories per day.

Compared to the caloric restriction diet, the intermittent fasting plus protein pacing diet significantly reduced sugar while increasing dietary fiber and protein.

Despite many differences, the diets were matched for calorie intake and calories burned through physical activity.

Participants self-reported their dietary intake daily, along with daily monitoring by researchers and weekly dietitian meetings.

Stool and blood samples were collected before, mid-intervention, and after the intervention to assess gut microbiome, cytokines, and metabolomic profiles. At the same intervals, participants completed a 15-question gastrointestinal symptom rating scale (GSRS).

The study authors compared these markers between the two groups to identify any significant differences in response to the two diets.

Benefits for weight management, gut health on both diets

The initial study trial reported that both groups saw significant improvements, however, the intermittent fasting plus protein pacing group witnessed greater improvements in their:

• weight
• total fat mass
• visceral fat mass
• desire to eat
• fat-free mass percentage.

The current analysis revealed significant changes in gut response to both diet interventions, but more prominent and beneficial shifts with the intermittent fasting plus protein pacing diet. These effects might help account for the diet’s observed weight management advantages.

Participants in the intermittent fasting plus protein pacing group experienced:

• notable improvements in gastrointestinal symptoms.
• a more substantial shift in gut microbiota.
• a greater overall change from baseline compared to the caloric restriction group.

The researchers noted increases in specific gut bacteria in the intermittent fasting and protein pacing group, particularly Christensenellaceae, which is associated with reduced visceral fat, improved fat oxidation, and enhanced metabolic health.

Additionally, intermittent fasting and protein pacing led to increased circulating amino acid metabolites favoring fat oxidation and cytokines linked to lipolysis (fat breakdown), weight loss, inflammation, and immune response.

Increases in amino acid-derived metabolites in participants’ gut microbiome following an intermittent fasting protein pacing regimen can support energy, protein synthesis, and the proliferation of hepatocytes [involved in nutrient metabolism].

While the intermittent fasting and protein pacing showed more significant benefits overall, the caloric restriction diet notably displayed an increase in metabolites associated with a longevity-related metabolic pathway.

The study also revealed a correlation between individuals’ gut microbiome composition and their level of weight loss in response to the diet interventions.

How intermittent fasting and protein pacing may improve gut, metabolic health

Bacteria that reside in the human gastrointestinal tract produce bioactive metabolites known to influence health.

The bacterial environment within the gut shifts based on its specific inputs. Essentially altering caloric consumption, fiber source and amino acid availability can influence the type of bacteria in our gut. In the [intermittent fasting and protein pacing], protein availability, spacing between meals and fasting windows were shown to have positive influence on microbial species.

Thomas M. Holland, MD, MS, a physician-scientist at the RUSH Institute for Healthy Aging, Rush University System for Health, who was not involved in the study, provided additional insight.

Holland noted that while it is difficult to pinpoint precisely why the intermittent fasting and protein pacing diet resulted in more significant beneficial outcomes than the caloric restriction diet, “the combination of intermittent fasting and meal replacement with protein shakes may be key factors.”

“The intermittent dietary input periods and the high protein content of the shakes likely promoted gut microbiome competition. Furthermore, the fiber in the shakes contribute[d] to better blood sugar control, reduced cholesterol absorption (leading to lower LDL levels and improved cardiovascular health), and enhanced general gut health, among other benefits.”

– Thomas M. Holland, MD, MS

“This is not to say that calorie restriction alone wasn’t beneficial; it just wasn’t as impactful,” he emphasized.

Hope for improving obesity management and precision nutrition

The study highlights differences in gut microbiome and circling metabolites connected to dietary interventions that facilitate weight loss and alterations in body composition. These findings could help shape future precision nutrition recommendations through larger and longer-duration clinical studies.

Specifically, combined intermittent fasting and protein-pacing dietary interventions may offer innovative approaches to achieving healthy weight management and improving overall health outcomes.

However, the long-term practicality and safety of this study’s particular approach to an intermittent fasting and protein-pacing diet is not well-explored.

When it comes to weight loss and gut health, it’s essential to consider precision medicine and individual differences. Depending on one’s starting body habits and goals, different diets will offer various benefits,” Dr Qaisar Ahmed said; he highlighted, “a more diverse gut microbiome improves digestion and nutrient absorption, which are beneficial for overall health, including brain and cardiovascular health.”

Thomas M. Holland concluded that both diet quantity and quality should be addressed for weight loss, ideally with guidance from a physician or registered dietitian.

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