PHYSICAL ACTIVITY AND LOW CARBOHYDRATE DIETS
Elena Tateo, MS RD
Melissa Bollman, MS, RD
CJ Segal-Isaacson, EdD, RD
Have you made exercising more one of your New Year’s resolutions? Whether you
enjoy running or are a devoted gardener, being active is essential for a healthy body
and mind. Below are the exercise guidelines for healthy adults issued by the American
College of Sports Medicine:
Exercise (be active) 3 to 5 days per week
Warm up 5 to 10 minutes before exercise
Maintain exercise intensity for 30 to 45 minutes
Gradually decrease intensity of workout then stretch and cool down for 5 to
While this may sound difficult to achieve, there are many ways to get or stay active.
Here is a list of some common activities and the estimated calories burned for each 30
minutes of activity.
Calories expended in 30
Calories expended in 30
minutes Male (175 lbs)
minutes Female (135 lbs)
Biking 12-13.9 mph (moderate
Stretching, hatha yoga
Dancing – general
Dancing - ballet, modern
House Cleaning – vigorous
(mop, wash car)
House Cleaning – light
Playing w/ kids moderate -
Mowing lawn - Hand mower
Running - 6 mph
Basketball – Game
Walking - 4 mph, level surface 167
Walking – leisure
Canoeing/Rowing – moderate 292
Swimming laps freestyle –
* Data from ACSM Resource Manual for Guidelines for Exercise Testing and Prescription Third Edition. Chart adapted from Georgia
State University website.1
If you can’t fit all of your exercise into one interval, doing 10-15 minute bouts three to
four times a day is good too. Staying active by gardening, housework, mowing, walking
briskly and climbing stairs all count towards achieving your weekly activity goals.
If you are regularly exercising at moderate or high intensities (cycling, running, jogging,
etc.) you may want to see whether "preloading" with a small amount of carbohydrates
one to two hours before you exercise enhances your performance. High intensity
activity is defined as greater than 85% of your maximum heart rate while moderate
activity is defined as 70-85% of your maximum heart rate. Alternatively, you may want
to have some carbs after you exercise to help replenish your body’s supply of stored
carbohydrates (glycogen) in the liver and muscles. Pre or post loading is not necessary
for lower intensity exercise such as walking.
If your main goal is weight loss, it is a good idea to find several types of activities you
enjoy and create a regular weekly routine where you alternate between them. The
advantage of this is that the variety both helps keep things more interesting and works
different sets of muscles which in turn more fully develops your physique. Varying the
exercise routine also helps to minimize the risk of injury by allowing one set of muscles
to recover while exercising other sets. A balance of aerobic, strength and flexibility
exercises in combination with a healthy diet will maximally increase your health and
If you are new or returning to exercising, gradually work your way up to the point where
you can sustain a moderate to high exercise intensity for at least 20-30 minutes to
maximize calorie expenditure. Even though this has been said many times before, it
bears repeating: It’s an excellent idea to consult with your primary care provider before
you begin any new exercise program, especially if you have a history of heart disease,
stroke, diabetes or hypertension.
Finally, it’s important to always to warm up before exercise and stay adequately
hydrated during longer bouts of exercise (see Table 1). Consider taking a multi-vitamin
and mineral supplement, especially if you have also reduced your caloric intake.
Table 1: Guidelines for Hydration during Moderate to High Intensity Exercise
• Before exercise: Consume 4-8 ounces of cool fluids.
• During exercise: Consume 4-8 ounces of cool fluids every 15-20 minutes
• After exercise: Consume 8-16 ounces of cool fluids.
• Increase fluid intake for hot and humid weather.
• You can also weigh yourself before and after exercise and consume 16
ounces of fluids for every pound lost during exercise.
One last note... Professional and amateur bodybuilders have long experimented with
modified versions of ketogenic diets. A subset of bodybuilders has used targeted and
cyclical ketogenic diets for some time to achieve their goals of increasing muscle mass
and decreasing body fat. The targeted ketogenic diet differs from a standard ketogenic
or low carb diet because carbohydrates are consumed at specific times around
exercise. The cyclical ketogenic diet alternates a low carb diet with a low fat diet on a
weekly basis. A common pattern is to maintain a low carb diet Monday through Friday
and a low fat diet on Saturday and Sunday. The types of exercise during these two
phases will be varied too. During the low carb phase the body builder will do somewhat
lower intensity and aerobic exercise to maximally burn body fat. During the low fat
phase the exercise routine is ratcheted up to high intensity to build muscle. The low fat
phase also allows muscles to refill their glycogen stores.2
Endurance athletes have historically used high carbohydrate diets during training to
enhance performance and delay the onset of exhaustion. However, a study by Phinney
et al. published in 1983 showed that after an adaptation period, a low-carb, high-fat diet
could result in better rather than worse endurance performance.3 Phinney et al.
observed five trained cyclists consuming a weight-maintenance diet that contained only
20 grams of carb per day and concluded that aerobic endurance exercise by well-
trained cyclists was not compromised by four weeks of ketosis, suggesting a dramatic
adaptation that conserved carbohydrate fuel sources --- both glucose and muscle
Phinney et al. also looked at slightly to moderately overweight, untrained individuals
who consumed a very low calorie ketogenic diet, supplemented with protein, fluid,
vitamins and minerals.4The conclusion was that prolonged moderate endurance
exercise (treadmill walking) can be successfully performed, but not optimally, until after
an adaptation period to the ketogenic diet of greater than one week and possibly six
weeks or more.
We wish you a healthy and happy New Year from the staff here at CCARBS! Drop us a
line and let us know how you are doing and feel free to ask us more about exercise!
1. Data from ACSM Resource Manual for Guidelines for Exercise Testing and
Prescription Third Edition. Chart adapted from Georgia State University website.
2. Mcdonald, L. The Ketogenic Diet: A complete guide for the dieter and
practitioner. 1998. Chapter 11 and 12.
3. Phinney, S.D., Bistrian, B.R., Evans, W.J., Gervino, E., Blackburn, G.L. The
human metabolic response to chronic ketosis without caloric restriction:
preservation of submaximal exercise capability with reduced carbohydrate
oxidation. Metabolism. 1983. 32, no. 8: 769 – 776.
4. Phinney, SD, Horton, ES, Sims, EAH, Hanson, JS, Danforth, E, Jr., LaGrange,
BM. Capacity for moderate exercise in obese subjects after adaptation to a
hypocaloric, ketogenic diet. J. Clin. Invest. 1980. 66: 1152 – 1161.