It is commonly thought that pets can just be fed less of their regular food during a weight loss program. Unfortunately, this is not the case. Regular adult maintenance foods are generally lacking in the special needs qualities that are found in diet foods.
In order to lose weight, a dieter must eat fewer calories than necessary to support ideal weight. This undernourished state requires that the body use the energy stored in fat. The switch to stored energy also requires that the body use proteins.
The amino acids in protein are used to make sugar to feed the nervous system and the heart muscle and are necessary to use fat energy. The storage form of protein is muscle, and dieters lose muscle as well as fat during a diet. Studies in humans, dogs and other animals confirm that weight loss foods that are high in protein decrease this muscle loss and increase fat loss during a diet.
Feeding dogs 39-40 percent of their calories in protein, and cats 46-50 percent of their calories in protein has proven to be effective for decreasing muscle loss. The animal also uses 25 percent of its own calories during the process of digesting the protein in food. This energy expenditure to digest protein aids in further weight loss.
Human subjects have found high protein weight loss diets to be more satisfying and consequently will voluntarily eat less food. Although not proven in cats and dogs, experimental evidence suggests the same satisfying effect of high protein diet pet foods.
As the stomach fills with food during a meal, it enlarges or distends. This “stretching” causes the release of hormones into the blood stream, from which point they travel to the appetite center of the brain, setting off the signals for fullness or satiation. This effect continues as food moves from the stomach and fills the intestines.
By increasing the amount of indigestible fiber in diet food, fewer calories can be fed while causing the same stomach and intestinal distension and releasing the same hormones. The brain receives a signal of satiation despite the ingestion of fewer calories. Human studies confirm this effect and animal studies are very suggestive. Owners report decreased begging behavior when pets are dieted on high fiber diets.
The purpose of a diet is to lose fat, so feeding excess fat makes little sense. Fat contains more than twice the calories per gram than protein and carbohydrates. The body does need fat, especially the essential omega-3 and omega-6 fatty acids, but more than the essential amounts only adds calories to the diet - 40 calories per teaspoon to be exact (no matter what kind of fat or oil!).
In addition to reducing the nutrient value of the meal, fat also reduces the size of each meal, and dieters don’t appreciate that. Additionally, fat only uses 2-3 percent of its own calories during digestion, leaving the rest of the fat to be absorbed and stored in the body!
Added Vitamins and Minerals
The dieting body can tolerate fewer calories than necessary for its ideal weight. The same is not true of vitamins and minerals. Limiting the calories of regular food also limits necessary vitamins and minerals. Fortifying diet food with vitamins and minerals ensures adequate intake of these nutrients despite the decreased meal size.
Regular pet foods do not meet any of the above qualities. In fact, animals that are dieting on adult maintenance formulas would suffer deficiencies in essential amino acids, vitamins, and minerals.
Over the counter weight control foods are no better. To begin, they are formulated for use without veterinary supervision. The 95 or so weight control foods available for cats and dogs meet few of the above requirements, so their calorie restriction is typically inadequate for successful weight loss. The protein content of these foods is rarely higher than regular food and the fiber content is variable. Few claim any vitamin or mineral fortification.
So what are the perfect diet foods for pets? For a serious weight loss program there are only two quality alternatives.
The first is a veterinary formulated and approved weight loss diet. There are several brands to choose from. These products are designed to be convenient to use while addressing the needs of the dieting pet.
The second is a homemade diet that is specially formulated to meet these same demands. Although more expensive and less convenient, homemade diets are tastier and more satisfying than their commercial counterparts. An added benefit is that the extra expense and commitment required by the owner fosters greater compliance with the weight loss program. Homemade diets also allow for greater manipulation of ingredients to address the changing needs of the dieting pet.
If you are undecided, your veterinarian can help you chose the best alternative for you and your pet.
Dr. Ken Tudor