Biomedical subjects

David Raubenheimer

Publications and source records attributed to David Raubenheimer.

6 recordsLinked to original sources

PubMed2006

Evolving resistance to obesity in an insect.

Failure to adapt to a changing nutritional environment comes at a cost, as evidenced by the modern human obesity crisis. Consumption of energy-rich diets can lead to obesity and is associated with deleterious consequences not only in humans but also in many other animals, including insects. The question thus arises whether animals restricted over multiple generations to high-energy diets can evolve mechanisms to limit the deposition of adverse levels of body fat. We show that Plutella xylostella caterpillars reared for multiple generations on carbohydrate-rich foods (either a chemically defined artificial diet or a high-starch Arabidopsis mutant) progressively developed the ability to eat excess carbohydrate without laying it down as fat, providing strong evidence that excess fat storage has a fitness cost. In contrast, caterpillars reared in carbohydrate-scarce environments (a chemically defined artificial diet or a low-starch Arabidopsis mutant) had a greater propensity to store ingested carbohydrate as fat. Additionally, insects reared on the low-starch Arabidopsis mutant evolved a preference for laying their eggs on this plant, whereas those selected on the high-starch Arabidopsis mutant showed no preference. Our results provide an experimental example of metabolic adaptation in the face of changes in the nutritional environment and suggest that changes in plant macronutrient profiles may promote host-associated population divergence.

Adipose Tissue↗

PubMed2005

Nutrient-specific foraging in invertebrate predators.

Many herbivores and omnivores adjust their food selection behavior to regulate the intake of multiple nutrients. Carnivores, however, are generally assumed to optimize the rate of prey capture rather than select prey according to nutrient composition. We showed experimentally that invertebrate predators can forage selectively for protein and lipids to redress specific nutritional imbalances. This selection can take place at different stages of prey handling: The predator may select among foods of different nutritional composition, eat more of a prey if it is rich in nutrients that the predator is deficient in, or extract specific nutrients from a single prey item.

Animals↗

PubMed2004

A comparison of nutrient regulation between solitarious and gregarious phases of the specialist caterpillar, Spodoptera exempta (Walker).

Nutritional regulatory responses were compared between solitarious and gregarious phases of the African armyworm, Spodoptera exempta. When allowed to mix between two nutritionally imbalanced but complementary foods, final-instar caterpillars in both phases selected a diet comprising more carbohydrate than protein. This contrasts with other larval lepidopterans studied to date. Only minor differences were found in the position of the intake target for the two phases, despite their different energetic requirements for migration as adults. When restricted to nutritionally imbalanced diets, caterpillars of both phases were less disposed to overeat protein on high-protein diets than carbohydrate on high-carbohydrate diets, relative to the self-composed intake target. However, in both cases gregarious larvae overingested the excess nutrient to a greater degree than did solitarious larvae. Furthermore, gregarious larvae showed higher nitrogen conversion efficiency on an extreme protein-limiting diet, and accumulated more lipid per amount of carbohydrate consumed on carbohydrate-deficient diets. These phase-associated nutritional differences are consistent with the life-history strategies of the two phases.

Animals↗

PubMed2003

A correlation between macronutrient balancing and insect host-plant range: evidence from the specialist caterpillar Spodoptera exempta (Walker).

In an earlier study, we showed that the ingestive responses of the generalist caterpillar Spodoptera littoralis to foods imbalanced in their protein:carbohydrate content is similar to generalist locusts, but differs from that of specialist-feeding locusts. Here we further pursued the comparison by repeating the experiments using a closely related specialist caterpillar, Spodoptera exempta. First, caterpillars were allowed to self-compose a diet of preferred protein:carbohydrate balance by mixing between nutritionally complementary foods. Then, they were confined to one of five imbalanced foods, in which we measured the trade-off between over- and under-ingesting the two nutrients. On complementary foods, the caterpillars actively regulated their protein and carbohydrate intake. In the no-choice experiment, those fed excess-protein foods ingested small surpluses of protein compared with generalist feeders, thus showing a pattern of nutrient balancing similar to that observed in specialist locusts. Utilisation data indicated that ingested excesses and deficits were to some extent offset by differential utilisation. Evidence also showed that post-ingestive responses of the specialist S. exempta were less flexible than those observed in the generalist S. littoralis, a pattern which is again in accordance with comparisons of acridids differing in their host-plant range.

Animals↗

PubMed2003

Ontogenetic changes in the rate of ingestion and estimates of food consumption in fourth and fifth instar Helicoverpa armigera caterpillars.

We present the second in a series of experiments investigating the behavioural mechanisms used by Helicoverpa armigera caterpillars to fund the increased nutrient requirements associated with growth and development. In the work reported here, we measured ontogenetic changes in the rate of ingestion (amount of an artificial food ingested per unit time when the insect is actually feeding) in fourth and fifth (penultimate and ultimate) instar caterpillars. These data are used together with those obtained in a previous study on ontogenetic changes in the proportion of time spent feeding to estimate the total amount of food ingested over three 33.3% temporal segments of the period from ecdysis to the cessation of feeding in the two stadia. Overall, the rate of ingestion in the fifth stadium was about three times that in the fourth. Rate of ingestion was constant over the fourth stadium but increased over the course of the fifth. Total consumption in the fifth stadium was about 3.5 times greater than in the fourth, mainly due to the greater rate of ingestion. In the fourth stadium, consumption in the third segment was greater than in either of the first two segments because the time spent feeding was greater. In the fifth stadium, consumption in the second segment was greater than in the first because of an increase in time spent feeding. In contrast, the greater intake in the third segment as compared with the second was due to an increase in the rate of ingestion. Our results demonstrated that the larvae, through increasing the rate of ingestion, were able to satisfy their increasing nutritional requirements without there being, necessarily, a commensurate increase in the time spent feeding.

Animals↗

PubMed2003

Geometric analysis of macronutrient intake in humans: the power of protein?

We introduce a state-space, geometrical approach that has previously been derived and tested using non-human animals and aim to demonstrate that it has the potential to generate testable hypotheses and provide novel insights into human nutrition and diet selection. This 'Geometric Framework' is unusual in that it focuses on the interactions between dietary constituents, and thus emphasizes the manner in which organisms regulate the balance of nutrients ingested. We report results from a pilot study, which indicate that protein ingestion is more strongly regulated than carbohydrate+fat. On the basis of these results and a brief survey of other experimental and population-level data, we hypothesize that regulation of protein intake may explain more of the modern human nutritional condition than has previously been appreciated.

Animals↗