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Dean Pomerleau posted a topic in CR Science & TheoryOver on this thread, Rodney wrote: Have you decided whether or not to actually calorie restrict Paloma? I restrict my dog Zoe, and that's one reason I suspect she is always scrounging for food as well. Specifically, I limit her food to 80g/day, about 10% below the 90g/day recommended on the package for active dogs her size (11lbs) - she gets a lot of exercise for a small dog since she runs around while my wife and I walk her > 3 miles per day, which is long way for a small dog. From the dog food package, that amount of dog food equates to about 28 kcal / lb of bodyweight per day. If scaled to a 115lbs person like me - that would be about 3200 kcal/day, which is quite close to what I eat, when you factor in metabolizable energy! Interestingly, this 28kcal / lb BW per day is exactly the same amount of food fed to the control group of Labradors in the dog CR studies  that Al posted about recently, conducted by the Ralston Purina company about a decade ago. Unfortunately, the poor Labs were likely pretty sedentary, kept in cages their entire lives, without opportunity to take walks . From : Dogs were housed in 2 X 19-m indoor-outdoor kennel runs with concrete floors for 8 years. The amount of exercise the dogs received was not controlled. According to the package on our dog food, relatively sedentary dogs should get only 66% as many calories as active dogs (e.g. 60g/day instead of 90g/day for a dog Zoe's size, or 18.66 kcal / lb BW per day). Plus, to make things even worse for the poor caged & sedentary Labs, the control dogs were fed ad lib from weaning until age 3.25 years - over 1/4 of their entire lifespan. Labs are fully grown and are supposed to have reached their adult weight by 2 years old, so the control dogs were fed ad lib until well into adulthood. In contrast, each CR dog was paired with one of the control dogs (of the same gender - 2/3rd were female), and fed 25% less than their pair-mate from weaning until death, so 25% less than ad lib for the first 3.25 years, and 21 kcal / lb BW per day - which is still above the 18.66kcal/lb BW recommended for sedentary dogs! The fact that they were fed ad lib until well past maturity, and likely had a sedentary lifestyle and so were overfed throughout their life by usual dog calorie recommendations, is reflected in the control dogs' weight. They don't have the weight trajectory data for the dogs, but by the 8th year the control dogs weighed an average of 74 lbs, which is 40% more than the CR dogs, who weighed 53 lbs on average. From here, the healthy weight range for female Labs (since these were mostly females) is 55-70 lbs. I'm not sure what the definition of obesity would be for relatively sedentary Labradors, but the control dogs were above the healthy weight range, and the CR dogs were right around the bottom end of the healthy range. So the control group might be the equivalent of about a human BMI of 26-27 (overweight but not quite obese) and the CR group would be around a human BMI equivalent of 18-18.5, right around many CR practitioners. Rapid growth and too much weight is bad news for dogs (and for people), but especially for Labs, because they are prone to cancer and especially joint problems / osteoarthritis, which is exacerbated by too much food and/or too much weight. So what were the lifespan results? From , the CR dogs lived 17% longer on average compared to the control dogs (13 vs. 11.1 years mean lifespan). The longest lived dog was a CR female, who died at 14.5 years, which was 9% longer than the longest lived control dog, another female who lived to 13.29. So not a whole lot of difference in max lifespan. While not in the original paper , I've created a graph of the survival curves for the two groups of dogs from Table 1 in the full text (yes - call me crazy). Here it is: Given how few dogs there were in each group (only 24), those survival curves are amazingly smooth and well-behaved! They also bear a striking resemblance to the AL and 10% CR groups of rats in PMID 26695614 that I discussed here two days ago, the survival graph from which I've reproduced below: If you ignore the CR40 survival curve, the two remaining rat survival curves (AL and CR10) look a whole lot like those of the two dog groups. Recall in that study, the median survival of the CR10 rats was 14% longer, and the median survival of the CR40 rats was 19% longer than AL-fed controls. In the dogs, the CR25 survival advantage was 17% relative to controls, right in the middle. Amazingly consistent! Given the striking similarity between the dog and the rat data, it would seem reasonable to extrapolate the dog data to predict that if there had been a CR10 group of dogs, they would have enjoyed a small bit less life extension relative to the CR25 dogs (e.g.. ~14% median life extension vs. 17% for CR25), and if there had been a CR40 group of dogs, they might have enjoyed a small bit more life extension relative to the CR25 dogs (e.g. ~19% vs. 17% median life extension for CR25). Put another way - the control dogs in this study were fed too much, given their caged lifestyle, so they grew fat. The CR dogs were fed an amount commensurate (or a bit higher) than is recommended by dog nutrition experts, remained slim and lived 17% longer than controls, enjoying nearly as much CR longevity benefit as can be hoped for in mammals, based on the rat data from PMID 26695614 discussed here. Bottom line? It appears from the rat, dog and primate CR data, that most of the CR benefits for the average animal come from avoiding overweight/obesity. Severe CR appears to provide seriously diminishing (perhaps negligible) marginal returns in terms of median lifespan, and may come at the cost of increased early mortality (based on the aforementioned rat data), and IMO probably not worth the risk given the disappointing 9% max lifespan advantage seen in the CR25 dogs relative to overweight controls. So my plan for myself and Zoe is to remain very active and eat only enough to stay quite slim. That way we both may be able to garner some CR benefits, and perhaps I at least can remain in good health long enough to be around for the arrival of longevity escape velocity, hopefully in several decades if we're lucky. Zoe is 5 years old. While her breed (Havanese) is long-lived for dogs (typically 13-15 years), she is unlikely to be around long enough to live forever. Perhaps I'll clone her or cryopreserve her, if either technology improves and comes down in price quickly enough. --Dean -----------  J Am Vet Med Assoc. 2000 Dec 1;217(11):1678-80. Evaluation of the effect of limited food consumption on radiographic evidence of osteoarthritis in dogs. Kealy RD(1), Lawler DF, Ballam JM, Lust G, Biery DN, Smith GK, Mantz SL. Author information: (1)Pet Nutrition Research Department, Ralston Purina Company, St Louis, MO 63164, USA. Free full text: https://www.avma.org/News/Journals/Collections/Documents/javma_217_11_1678.pdf OBJECTIVE: To determine prevalence of radiographic evidence of osteoarthritis in 4 diarthrodial joints of dogs with restricted feed intake, compared with dogs without restricted feed intake. DESIGN: Paired feeding study. ANIMALS: 48 Labrador Retrievers. PROCEDURE: Dogs in litters from 7 dams and 2 sires were paired by sex and weight within litters and randomly assigned to a control-fed group or a limit-fed group that received 25% less food than the control-fed group. Radiographic evaluation of prevalence and severity of osteoarthritis in the hip, shoulder, elbow, and stifle joints was performed when dogs were 8 years of age. RESULTS: Radiographic evidence of osteoarthritis that affected multiple joints was significantly more common in the control-fed group than in the limit-fed group. Prevalence of lesions in the hip joint was 15/22 in the control-fed group and 3/21 in the limit-fed group. Prevalence of lesions in the shoulder joint was 19/22 in the control-fed group and 12/21 in the limit-fed group; lesions in this joint were generally mild. Severity, but not prevalence, of osteoarthritis in the elbow joint was greater in the control-fed group than in the limit-fed group. CONCLUSIONS AND CLINICAL RELEVANCE: Prevalence and severity of osteoarthritis in several joints was less in dogs with long-term reduced food intake, compared with control dogs. Food intake is an environmental factor that may have a profound effect on development of osteoarthritis in dogs. PMID: 11110459 --------------  J Am Vet Med Assoc. 2005 Jan 15;226(2):225-31. Influence of lifetime food restriction on causes, time, and predictors of death in dogs. Lawler DF(1), Evans RH, Larson BT, Spitznagel EL, Ellersieck MR, Kealy RD. Author information: (1)Néstle Purina PetCare Research, 835 S 8th St, St Louis, MO 63164, USA. Free full text: https://www.avma.org/News/Journals/Collections/Documents/javma_226_2_225.pdf OBJECTIVE: To describe effects of lifetime food restriction on causes of death and the association between body-mass characteristics and time of death in dogs. DESIGN: Paired-feeding study. ANIMALS: 48 dogs from 7 litters. PROCEDURES: Dogs were paired, and 1 dog in each pair was fed 25% less food than its pair mate from 8 weeks of age until death. Numerous morphometric and physiologic measures were obtained at various intervals throughout life. Associations of feeding group to time and causes of death were evaluated, along with important associated factors such as body composition components and insulin-glucose responses. RESULTS: Median life span was significantly longer for the group that was fed 25% less food, whereas causes of death were generally similar between the 2 feeding groups. High body-fat mass and declining lean mass significantly predicted death 1 year prior to death, and lean body composition was associated with metabolic responses that appeared to be integrally involved in health and longevity. CONCLUSIONS AND CLINICAL RELEVANCE: Results were similar to results of diet restriction studies in rodents and primates, reflecting delayed death from species- and strain-specific intrinsic causes. Clinicians should be aware that unplanned body mass changes during mid- and later life of dogs may indicate the need for thorough clinical evaluation. PMID: 15706972