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Exercising first thing in the morning can improve postprandial plasmatriglyceride levels throughout the day, according to a study by researchers atthe University of Colorado Health Sciences Center in Denver. Lead author TracyHorton, PhD, assistant professor of pediatrics, presented the findings at the2005 Annual Scientific Meeting of NAASO, The Obesity Society (formerly theNorth American Association for the Study of Obesity), held October15–19, in Vancouver, British Columbia.
Eleven men and eight women, all in good health, took part in 2 separatestudy days involving 1 day with exercise and 1 day during which participantsremained sedentary. Each study day was preceded by 5 days of diet control and60 hours of inactivity. Participants' body mass index was 20–27. Thestudy's purpose was to determine the impact of a single, early morning bout ofexercise on triglycerides as they circulate through the blood over the courseof the day.
On the exercise day, participants walked on a treadmill at a slight inclinefor 1 hour, from 7:15 a.m. to 8:15 a.m., at moderate intensity. They atebreakfast at 8:30 a.m., lunch at 12:30 p.m., and dinner at 5:30 p.m. Previousstudies have looked at postprandial triglyceride levels 12–16 hoursafter a meal high in fat, Horton explains. In this study, participants ate amore "normal" diet comprising 34% fat, 15% protein, and 51%carbohydrate. Blood samples were drawn prior to exercise, 20 minutes aftereach meal, and at various times throughout the day.
Accumulated benefits of early morning exercise were shown in the overalltriglyceride levels when compared with the sedentary day. After 13 bloodtests, the integrated area under the curve for total triglycerides from theprebreakfast draw to the final draw at 10:30 p.m. was 20,199 mg/dl/840 min onthe exercise day and 27,421 mg/dl/840 min on the sedentary day. (Primary carephysicians are used to seeing fasting triglyceride levels. The values used bythe authors reflected levels seen over the course of the day as lipids werebeing metabolized.)
No benefit was seen at the postbreakfast draw (3,910 mg/dl/240 min vs.3,619 mg/dl/240 min), but it became evident in later blood samples asexercise-day triglyceride levels began to drop relative to those of thesedentary day. Following lunch, exercise-day levels were 8,517 mg/dl/300 min,compared with 10,367 mg/dl/300 min on sedentary day. Blood samples taken 5hours after dinner again showed the benefits of exercising versus beingsedentary (7,773 mg/dl/300 min vs. 13,436 mg/dl/300 min).
"Even your small, daily routine can keep lipids down a little; butthe more sedentary you are, the worse it gets," Horton says."Exercise is multibeneficial, and this is just one other reason toincorporate exercise into yourlifestyle."
Most clinicians only look at what's going on with fasting triglycerideswhen prescribing lipid-lowering drugs, but not at what's happening after ameal, she explains. "Exercise is obviously a nondrug lifestyleintervention that has many benefits."
TURNING DATA INTO PRACTICE
Holly Wyatt, MD, an endocrinologist at the University of Colorado HealthSciences Center, agrees that studies like Horton's show the benefit ofexercise, but she says not enough is known about how the timing of activityaffects achieving exercise goals. Consistency in exercise—finding aregimen at a time and intensity level one can stick with—"is byfar the number one thing that needs to happen," she says.
"In general, the data support getting exercise," Wyattcontinues. "Overriding any of the data is what is the most likely timeyou'll consistently do it."
Motivation is a real problem, and the debate over duration and intensitydoes little to resolve the growing rate of obesity, she says. Translating datato the community is where primary care clinicians can help.
"Start the patient out with baby steps with a pedometer," Wyattsuggests. "When a patient hears 10 or 12 thousand steps a day, itbecomes overwhelming. [By] beginning with 3 thousand and working up gradually,they can see they've accomplished something and are encouraged to do a littlemore."
Even 30 minutes three times a week can be too much for those used to asedentary lifestyle. "With my patients, I take their day planner andlook for sedentary times," Wyatt says. "Soccer moms take theirkids to practice. Instead of sitting on the side during practice, why not walkaround the field? Or during TV commercials, get up and walk. They're littlethings, but they add up." 
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