What’s More Important: Diet or How Much You Exercise?

You have probably wondered at some point in your life, is diet more important than exercise or does exercise trump diet. I think the question that you first need to ask yourself is: “What is your main outcome or goal?” If your answer is strictly weight loss, both diet and exercise are important but the focus placed on diet is slightly higher. If you’re looking to just maintain a healthy lifestyle then you need to consistently monitor and focus on both. Remember, you can’t manage something if you don’t measure it. Finally, if you’re someone who has lost a significant amount of weight and your goal is to maintain that weight loss for the rest of your life then both diet and exercise are your best friends.

One of the best research-based organizations that looks at these types of questions and more is the National Weight Control Registry (NWCR). The NWCR is the brain-child of Rena Wing, PhD, from Brown University Medical School and James Hill, PhD, from the University of Colorado. The NWCR “provides information about the strategies used by successful weight loss maintainers to achieve and maintain long-term weight loss.” The NWCR is currently tracking over 10,000 individuals who have lost significant amounts of weight and, most importantly, have kept it off for long periods of time.

NWCR members have lost an average of 72.6 pounds and maintained the loss for more than 5 years. “To maintain their weight loss, members report engaging in high levels of physical activity (≈1 h/day/walking), eating a low-calorie, low-fat diet, eating breakfast regularly, self-monitoring weight, and maintaining a consistent eating pattern across weekdays and weekends.”

What should help clear up this debate is the fact that only 1 percent of the huge NWCR database (>10,000 subjects) have been successful at keeping their weight off with exercise alone. About 10 percent of the subjects have been successful with weight-loss maintenance by focusing on diet alone. More than 89 percent of the subjects have been successful because of BOTH diet and exercise modifications.

Your best bet is to spend quality time at the gym a few times a week and remember to challenge yourself when you’re moving through your paces. Stay active throughout the week and especially during the weekends. Focus on eating clean, healthy foods, avoiding highly processed foods while watching the added sugar in everything you eat. Finally, know that diet and exercise are your best choices to help get you there and once you’ve reached your goals, will help keep you there!


Wing RR, Hill JO. Successful weight loss maintenance. Annu Rev Nutr 2001;21:323–41.

Wing RR, Phelan S. Long-term weight loss maintenance. Am J Clin Nutr 2005; 82(1): 222S-225S.

What Can Some of the Classic Exercise Studies Teach Us?

imagesAs an exercise physiologist I have always been intrigued by what some of the classic exercise research studies have shown us. As a result, we have a large pool of data that offers us a better understanding of all the positive effects exercise can have on our body and overall health. Here are four studies that demonstrate this.

Harvard Alumni Study (started 1962)

The Harvard Alumni Study was one of the first epidemiologic studies to examine the relationship between physical activity and incidence of heart attack. The studies lead investigator was Ralph Paffenbarger, Jr., MD, DrPH, DScSubjects who participated in the study were male surviving alumni who enrolled in Harvard University between 1916 and 1950, and were mailed brief questionnaires in 1962 and 1966, and 16,936 men responded (71% response rate). Results of the Study: The data showed that the relative risk for an alumni’s first heart attack increased for those who climbed less than 50 stairs a day compared to those who climbed fifty or more by 1.25 (one flight of stairs = 10 steps). For men who walked less than five city blocks daily, their relative risk for first heart attack was 1.26 times greater when compared to men who walked more than five blocks a day. Older men should expend at least 4200 kJ/wk (1004 calories/wk) in total physical activity to potentially reduce their risk of CHD by about 20%. Those expending 2100 to 4199 kJ/wk (502 calories – 1004 calories/wk), slightly lower than that recommended by the Surgeon General, had a possible nonsignificant 10% reduction in the risk of CHD. Total physical activity and vigorous activities showed the strongest reductions in coronary heart disease risk.

Dallas Bed Rest Study (started 1966) – 30-Year Follow-up

This study looked to assess the effect of a 30-year interval on body composition and cardiovascular response to acute exercise in 5 healthy subjects originally evaluated in 1966. Results of the Study: A 30-year follow-up showed body weight increased by 30%, percent body fat increased 100% (14% versus 28%), and there was little change in lean muscle mass (66 versus 72 kg). On average, V̇O2max decreased 11%, maximal heart rate declined 6% (193 versus 181 bpm) and maximal stroke volume increased 16%. There was no difference observed in maximal cardiac output (20.0 versus 21.4 L/min) and maximal AV oxygen difference declined 15% accounting for the entire decrease in cardiovascular capacity. Most notably, 3 weeks of bedrest in these same men at 20 years of age (1966) had a more profound impact on physical work capacity than did 3 decades of aging. Finally, an association was seen between physical activity and cardiovascular capacity, suggesting that physical inactivity accounts for as much as 40% of the age-related decline in maximal oxygen uptake.

Heritage Family Study (started 1992)

The Heritage Family Study consortium is composed of research teams from the following five institutions: Indiana University, University of Minnesota, Texas A&M University, Washington University and the Pennington Biomedical Research Center. The consortium was founded by Claude Bouchard, Ph.D who was then on the faculty at Laval University in Quebec City. The purpose for the study was: (1) regular endurance exercise has favorable effects on the risk profile for CVD and type 2 diabetes; (2) there are individual differences in the response to regular exercise; and (3) genes are thought to play a very important role in determining the benefits we receive from regular physical activity. The main goal of the project is to study the role of the genotype in the cardiovascular and metabolic responses to aerobic exercise training and the changes brought about by regular exercise for several cardiovascular disease and diabetes risk factors. Results of the Study: There have been more than 120 papers published from this study since 2004. Research has demonstrated that with young or older adults, improvements in VO2max have ranged from almost 0% to 50%, even though subjects completed exactly the same exercise program under close supervision. There was a large variation in response to exercise training at each of the five centers in the Heritage Study. Although the average increase in VO2max was 19%, about 5% of the subjects had little or no change (<5%) and about 5% had an increase of 40 to >50%. This large variation occurred at all ages and at all levels of initial fitness and for women and men. There was about 2.5 times more variance between families than within families for the gains in VO2max, and the maximal heritability reached 47%. However, there was no relationship between initial level of VO2max and the change in VO2max after training (r = 0.08). In other words, it appears that one set of genes influenced the initial level and another set of genes influenced the response to training. Therefore, “part of the genetic component for VO2max expresses itself only in response to an active lifestyle” and researchers “could not find non-genetic variables measured before training that would differentiate between responders and non-responders.”

National Weight Control Registry (started 1994)

This group was founded by Rena Wing, Ph.D. from Brown Medical School, and James O. Hill, Ph.D. from the University of Colorado. It is considered the largest prospective investigation of long-term successful weight loss maintenance tracking more than 10,000 subjects who have lost significant amounts of weight (at least 30 pounds) and have kept it off for a considerable period of time. Each subject considers the following four items extremely important in helping them keep their weight off. Results of the Study:

  • 78% eat breakfast every day.
  • 75% weigh themselves at least once a week.
  • 62% watch less than 10 hours of TV per week.
  • 90% exercise, on average, about 1 hour per day.

Finally, here is a classic 1996 paper by Blair and Connelly that will hopefully help pull it all together for you.