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Insulin-like growth factor-I (IGF-1) and caloric restriction

IGF-I has many metabolic effects associated with cell metabolism and growth (e.g., promoting amino acid uptake, enhancing protein synthesis, attenuating protein degradation and facilitating glucose and free fatty acid uptake). Nutritional status is a major factor influencing circulating IGF-I concentrations. This study aimed to characterize the IGF-I system response to acute caloric restriction and also to determine if two isocaloric diets with different ratios of carbohydrate (CHO) to fat altered the IGF-I system under conditions of caloric balance. A double-blind, placebo-controlled crossover design was used in which 27 subjects underwent three 48-hour experimental treatments:
1. Caloric restriction (~313 kcal/day),
2. CHO (4566 kcal: 1120g CHO, 0g fat), and
3. CHO/fat (4611 kcal: 835g CHO, 135g fat).
Blood was sampled periodically (six time points total) for IGF-I (total and free), IGF binding protein (BP) 1-4, insulin and glucose. The researchers found that free IGF-I and IGFBP-1 significantly decreased and seemed to be the most sensitive IGF-I system components to acute, severe caloric restriction. They did not find any significant changes in IGFBP-2, IGFBP-3 or IGFBP-4 during acute, severe caloric restriction over two days. The IGF-I system was relatively stable during caloric balance regardless of the macronutrient ratio of CHO to fat. Insulin and glucose were lower with caloric restriction but not different between CHO versus CHO/fat. The implications of this research are that changes in free IGF-1 and IGFBP-1 are reflective of an acute caloric-restrictive state. Energy repletion mitigates these changes in IGF-I system components. These alterations in the IGF-I system have the potential to reduce anabolic processes and cause loss of muscle mass. Their measurement may also be valuable in monitoring the response to re-feeding in those consuming suboptimal calories such as crash dieters. 

Yogurt consumption and metabolic health
Intake of dairy products may be associated with lower risk of cardiovascular disease and type 2 diabetes. In particular, fat-free or low-fat milk and milk products have been recommended by the Dietary Guidelines for Americans as one of the food groups for which consumption should be increased. However, few related epidemiological studies have differentiated between types of dairy products or focused specifically on yogurt. This study explored the relationship of yogurt consumption with metabolic profile among the adults involved in the Framingham Heart Study. Results showed that among the 6,526 middle-aged to older men and women, yogurt intake was associated with better overall diet quality, greater intakes of several shortfall nutrients and healthier metabolic profiles independent of overall diet quality.