4.4 Flashcards
(10 cards)
- What are some dietary interventions that can achieve calorie restriction?
Dietary interventions include traditional calorie restriction (e.g., reducing total food intake by ~50%), intermittent fasting (such as every-other-day fasting), time-restricted feeding (limiting food intake to specific hours of the day, e.g., no food after 3pm), and diets altering macronutrient ratios (e.g., ketogenic diets with minimal carbohydrates).
- How does ad libitum feeding serve as a control in calorie restriction studies?
In ad libitum feeding, animals have unrestricted access to food, which often leads to hyperphagia and obesity. This group serves as the control, allowing comparisons that reveal the benefits of reduced caloric intake on metabolism and longevity.
- What are some important caveats to consider when interpreting calorie restriction studies in model organisms?
Key caveats include differences in feeding protocols in laboratory settings versus the wild, species-specific responses to calorie restriction, potential stress induced by restricted feeding, the timing of nutrient delivery, genetic background variations, and challenges with extrapolating short-lived animal models (like rodents) to human aging.
- What challenges can arise specifically in calorie restriction studies using rodents?
Rodents often consume more food ad libitum than they would in nature, potentially exaggerating the benefits observed under calorie restriction. Additionally, strain, gender, and age differences, along with laboratory conditions, can influence results and limit direct translation to humans.
- What have studies in rats shown about the impact of calorie restriction on lifespan?
Studies in rats have demonstrated that calorie restriction can extend lifespan significantly. For example, calorie-restricted rats often live noticeably longer than controls, with some studies reporting increases in lifespan by reducing age-related diseases and delaying the onset of chronic conditions.
- How does calorie restriction affect healthspan and age-associated diseases in non-human primates?
In non-human primate studies, calorie restriction has been shown to extend healthspan by delaying the onset of age-related diseases such as cardiovascular disease, diabetes, and some cancers. A higher percentage of calorie-restricted animals remain free from age-related disorders compared to controls over time.
- What is a fasting mimicking diet (FMD) and what effect has it shown in mice?
The fasting mimicking diet (FMD) is a regimen that provides limited calories and controlled nutrient composition to mimic the effects of fasting. In mice, FMD has been shown to extend healthspan by reducing disease incidence and increasing survival rates compared to standard feeding protocols.
- How do modifications in macronutrient ratios (such as a ketogenic diet) relate to the effects of calorie restriction?
While a ketogenic diet focuses on very low carbohydrate intake and high fat, it can mimic some aspects of calorie restriction, including improved insulin sensitivity and reduced inflammation. However, its effects are driven by changes in nutrient composition in addition to overall caloric restriction.
- What overall metabolic benefits are observed with calorie restriction in animal models?
Calorie restriction in animal models consistently improves metabolic markers by reducing body weight and fat mass, enhancing insulin sensitivity and glucose tolerance, lowering cholesterol levels, and diminishing inflammation. These changes help reduce the risk of cardiovascular diseases, type 2 diabetes, and other chronic conditions.
- How do the findings from calorie restriction studies support its role in extending longevity?
Multiple studies—spanning rodents, non-human primates, and other models—have shown that calorie restriction delays the onset of age-related disorders and extends both lifespan and healthspan. The benefits include reduced incidence of cardiometabolic diseases, improved cellular repair, and lower oxidative stress, collectively contributing to a longer, healthier life.
