Tammy J. Owens, et al. 2014
Obesity is constantly growing pathology in domestic feline population, as well as in humans, and is associated with a four-fold risk of developing diabetes mellitus, in fact obesity plays a primary role in insulin resistance and glucose intolerance (with impaired insulin secretion associated with weight gain).
The addition of fiber is a common strategy used in obesity management because cats regulate food intake. Indeed, diets high in water or fiber reduce both energy density and calorie intake, and may be useful in prevention and treatment of both obesity and diabetes mellitus. Although some studies suggest that diets with low carbohydrate and high protein content may be advantageous in management of feline diabetes mellitus, the fiber types and their concentrations in those studies were not specified.
Equally, other commercial diets formulated for management of feline obesity or diabetes mellitus highlight an increased crude fibers content in their product guides, but they don’t provide the overall present value of total fiber and therefore not allowing a comparison (neither in absolute nor in relative terms of the specific components of fiber, such as insoluble dietary fiber, high-molecular-weight soluble dietary fiber, and low-molecular-weight soluble dietary fiber).
Given that the effects of fiber types are not uniform, quantification of fiber fractions is valuable. Fiber supplementation, particularly insoluble dietary fiber, may affect nutrient absorption and modulation of postprandial glycemic response, whereas short-chain fatty acid, produced by bacterial fermentation of soluble dietary fiber, supports beneficial colonic microbial populations, which are recognized as having a central role in controlling obesity.
The Owens et al. study, published in JAVMA 2014, takes into consideration different wet (n=12) and dry (n=10) diets for the management of obesity and diabetes mellitus in cats with the aim of providing more information on the composition and quantity of the dietary fiber included. This study confirms the negative correlation between the overall energy of commercial diets and the concentration of total fibers, in addition to the lower energy concentration present in the diets indicated for the treatment of obesity, compared to those for diabetes mellitus (discrepancy deriving from the different ratio between overall fibers, soluble dietary fibers and insoluble dietary fibers present in the diet).
However, the energy differences in the different food groups are not always due to a different fiber content, since the energy does not depend only on the fibers, but also on other substances, such as fat. Unfortunately, only some of the diets included in the study report the differentiation between the total fibers present in the food, the insoluble and the soluble fibers.
Although the list of ingredients contains sources of insoluble fiber (cellulose), soluble fiber (psyllium, fruit fiber and guar gum), mixed fiber (flax seed) and low molecular weight soluble fiber (fructooligosaccharides and inulin), quantitative information would also be useful. Although no differences were found between dry and wet foods when compared as groups, there are significant differences when examined individually. Canned diets have less total fiber than their dry counterparts. Again, from the present study, the diet subdivision on the basis of the concentration of crude fibers risks underestimating the concentration of total fibers and therefore leading to an overestimation of carbohydrates and consequently of the energy content. Considering the historical use of the concentration of raw fibers to distinguish low and high fiber diets and to estimate the concentration in carbohydrates, previous food recommendations based on these parameters could be inadequate and inaccurate to date. In fact, this study shows that using the concentration of crude fibers, instead of the concentration in total fibers, to estimate the quantity of carbohydrates of the metabolizable energy, can determine an overestimation of up to 21% of carbohydrates in all diets, of 35% in wet and 28% in dry diet for diabetes mellitus, 12% in wet and 17% in dry foods for obesity. This obviously emphasizes the importance of evaluation of total fibers concentration and their use in the calculation of carbohydrates to differentiate the various foods.
In conclusion, this study has demonstrated that the concentration and fiber composition of a diet plays a crucial role in the choice and efficacy of the diets used in the management of obese and diabetes mellitus cats. The different types of fibers have different physiological effects, some of which have yet to be better understood. It is therefore encouraged to evaluate the different components fibers of the diets, so that we can increasingly help the diet choice in different pathological conditions, improving their effectiveness for the well-being of our patients.