Diet and Physical Activity
The PPET Study: People and Pets Exercising
Robert F. Kushner,* Dawn Jackson Blatner,* Dennis E. Jewell,† and Kimberly Rudloff
KUSHNER, ROBERT F., DAWN JACKSON BLATNER,
DENNIS E. JEWELL, AND KIMBERLY RUDLOFF. The
PPET Study: people and pets exercising together. Obesity.
Objective: Obesity is a significant public health problem
that is affecting people and their pets. The human-compan-
ion animal bond and the role of pets in providing social
support provides a rationale framework for studying the
effectiveness of a combined people and pets (PP) exercising
together (PPET) weight loss program.
Research Methods and Procedures: Thirty-six pairs of
overweight or obese people with an obese pet (PP) and 56
overweight or obese people only (PO) participated in a
1-year prospective controlled weight loss study. In a group
format, people received dietary and physical activity coun-
seling, and dogs were fed a calorie-controlled prescription
diet. Physical activity was recorded using the physical ac-
tivity recall questionnaire.
Results: Completion rates at 1 year were 61% for the PP
group and 58% for the PO group. Mean weight losses at 12
months using last observation carried forward were 4.7%
(PP) and 5.2% (PO). Mean weight loss among the dogs was
15%. Time spent in physical activity increased in both
groups to 3.9 (PP) and 3.5 (PO) h/wk. Two-thirds of total
physical activity in the PP group was spent with the dogs.
Discussion: The PPET study is the first program to dem-
onstrate the effectiveness of a combined PP weight loss
program. This fresh approach to the dual obesity epidemic
builds on the human-companion animal bond. Consider-
ation of social support for weight loss of family members,
friends, and coworkers should be extended to include pets.
Key words: weight loss, companion animals, social sup-
port, physical activity
Societal and cultural changes over the past decades are
considered to be major contributors to the rising obesity
epidemic (1). For many people, the subtle decline in daily
physical activity along with eating patterns that allow in-
creased caloric intake have resulted in weight gain and
development of overweight or obesity. Currently, over 60%
of American adults are overweight or obese, whereas 15%
of adolescents are considered at risk for overweight (2).
Perhaps not surprisingly, the same factors that have led to
human obesity underlie the growing prevalence of obesity
among companion pets. By the latest estimate, one-quarter
of dogs and cats are considered obese (3). Moreover, over-
weight and obesity are associated with impaired health in
both species. To combat this problem, both public health
professionals and veterinarians have endorsed a proactive
approach that includes adoption of healthy changes in diet
and physical activity (4,5). Creative and fresh ideas are
needed to address these rising obesity rates. Because obesity
in both species shares common causes and treatment rec-
ommendations, would it be beneficial to join forces?people
and pets (PP)1?to treat the duel obesity epidemic?
There a multiple reasons to support a combined human-
pet program to address obesity. The beneficial impact of
companion animals on the physical, social, and psycholog-
ical health of people is well documented (6). This has been
particularly studied among patients with cardiovascular dis-
ease (7–9), aging and dementia (10,11), and those with
ambulatory disabilities (12). The positive effect of health
and well-being resulting from the interactions with a pet has
been called the human-companion animal bond (13).
The other important role that pets play in human health is
social support. Past studies conducted among communities
and obesity programs have repeatedly shown that social
Received for review November 9, 2005.
Accepted in final form July 24, 2006.
The costs of publication of this article were defrayed, in part, by the payment of page
charges. This article must, therefore, be hereby marked “advertisement” in accordance with
18 U.S.C. Section 1734 solely to indicate this fact.
*Wellness Institute, Northwestern Memorial Hospital, Chicago, Illinois; and †Hill’s Pet
Nutrition, Inc., Topeka, Kansas.
Address correspondence to Robert F. Kushner, Wellness Institute, Northwestern Memorial
Hospital, 150 East Huron, Suite 1100, Chicago, IL 60611.
Copyright © 2006 NAASO
1Nonstandard abbreviations: PP, people and pets; PO, people only; PAR, physical activity
recall; DRA, dog-related activity; LOCF, last observation carried forward; PPET, People
and Pets Exercising Together.
1762 OBESITY Vol. 14 No. 10 October 2006
support is one of the most powerful predictors of adoption
and maintenance of behavior change (14). This is primarily
based on the social learning theory that emphasizes mutual
influence between the individual and the environment
(15,16). In a study of nearly 20,000 respondents who par-
ticipated in the National Health and Nutrition Examination
Survey III, social relationships were significant predictors
for engagement in five lifestyle and preventive health be-
haviors related to cardiovascular disease: cigarette smoking,
participating in physical activity, consuming fruits and veg-
etables, having blood pressure checked, and having choles-
terol checked (17). The influence of social support on phys-
ical activity is particularly strong (18–20). In a survey of
3342 adults from six countries, the social environment was
found to be the strongest independent predictor of being
physically active (21). Those who perceive low social sup-
port from their personal environment, i.e., family, friends,
school, and workplace, were more than twice as likely to be
sedentary compared with those who reported high social
support from their personal environment. Wing and Jeffery
(22) evaluated the importance of social support within a
group weight loss program. They found that recruiting par-
ticipants with a team of three friends and treating them with
a strong social support intervention decreased the number of
dropouts and markedly increased the percentage of partici-
pants who maintained their weight loss in full over a
6-month follow-up period.
Incorporating household pets in a weight loss program
offers a potentially new and practical approach to both
human and pet obesity. Companion dogs provide a social
function. Animal companions are commonly perceived to
be a member of the family and share attributes of the living
environment (23). Companion dogs may also provide peo-
ple with a source of social stimulation that is typically
more constant and reliable than friends and coworkers (23).
This is particularly important for exercise because the pres-
ence of a partner is associated with physical activity (24),
and dogs will rarely discourage such behavior. Furthermore,
people walking with their dog experience more social con-
tact and longer conversations than when walking alone (13).
Dogs may also strengthen engagement in a weight loss
program by providing challenge support in the way of
encouragement and motivation (25). For many individ-
uals, a helping relationship is a strong incentive for par-
ticipation and goal setting. Furthermore, pet ownership is
widespread—it is currently estimated that 39% of U.S.
households have dogs as companion animals, whereas 34%
have cats (26). Therefore, the potential influence of pets in
providing social support provides a rational framework for
studying the possible benefits of pets in aiding weight loss
among obese people.
Thus, the purpose of this study was to assess the effec-
tiveness of a combined PP weight loss program where both
human participants and companion dogs were obese. This
people and pet social support condition was compared with
people alone who did not own a companion animal. We
hypothesized that dogs would serve as a social support
system for exercise, and people walking with their dogs
would lose more weight at 1 year than people walking
alone. Although not designed as a research question, all
dogs were placed on a therapeutic hypocaloric diet as part of
the combined PP program.
Research Methods and Procedures
A 1-year prospective, controlled trial was conducted at
the Wellness Institute at Northwestern Memorial Hospital
(Chicago, IL). Overweight and obese adults who owned an
obese dog (PP group) or did not own a dog [people only
(PO) group] were recruited in the Chicago area through
flyers, newspaper advertisements, and veterinary clinics.
After an initial telephone screen, participants attended an
orientation session where the study was explained, and
informed consent was signed. The trial was approved by the
institutional review board of Northwestern University and
Hill’s Institutional Animal Care and Use Committee.
For inclusion in the study, people had to be between 21
and 65 years old, have a BMI ? 25 kg/m2, be in good
general health, and have no limitations to exercise. They
had to be weight stable and not taking any medications that
would affect their weight for at least 2 months before the
start of the study. If they were pet owners (PP group), they
had to be concerned about their dog’s weight and willing to
participate in a weight loss program with their pet. The dogs
had to be between 1 and 6 years old, spayed or neutered, and
in good general health except for obesity. Obesity, defined
as 20% over ideal weight for breed, was determined by body
weight and the body condition score (5). The dogs could not
be on any weight management program or taking any med-
ications or supplements including vitamins, Prozyme, or
herbal treatments for 2 months before the study.
The PP and PO groups met separately in small group
sessions ranging from six to 12 participants. Groups met
weekly for the first 16 weeks (treatment phase), then once a
month at months 5, 6, 9, and 12 (maintenance phase). Group
sessions were led by a registered dietitian who instructed
participants in recognizing and adopting healthy eating,
exercise, and coping patterns (27), use of commercial meal
replacement products, strategies to reduce total calories and
tips on increasing physical activity, and behavioral change
techniques. Participants were directed to a target caloric
goal of ?1400 calories/d and guided to increase physical
activity to 20 to 30 minutes on most days of the week. Groups
were also given a walking kit handout that contained a variety
of facts, suggestions, and community resources.
The PPET Study: People and Pets Exercising Together, Kushner et al.
OBESITY Vol. 14 No. 10 October 20061763
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