What Affect Does Diet and BMI Have on Physical Fitness?


Recent studies have shown that the physical fitness of an individual can be a promising indicator in measuring health and risk for outcomes such as obesity, cardiovascular disease, diabetes, cancer, and skeletal health. (1) The World Health Organization (WHO) recommends children and adolescents between the ages of 5-17 should get at least 60 minutes a day of moderate-to vigorous-intensity physical activity. Regular physical activity is associated with many health benefits in children and can improve cardiorespiratory and muscular fitness, as well as bone health (4). It is noteworthy to promote regular physical activity because research shows that cardiorespiratory fitness levels are significantly associated with total body fat and abdominal adipose tissue. (1) Lower levels of cardiorespiratory and muscular fitness are associated with CVD risk factors. (1) And improvements in cardiorespiratory fitness have positive effects on things like depression, anxiety, self-esteem, and academic performance. (1)

Findings from a cross-sectional study done in South Carolina found that children who are obese generally spend less time in moderate and vigorous physical activity than non-obese children. (2) It also found that the energy density of a child or adolescent’s diet is directly associated with fat intake, and both energy dense high-fat diets are associated with obesity. (2) In past studies it has been suggested that reducing dietary ED by combining increased fruit and vegetable intake, as well as decreasing total fat intake, was seen to control hunger and be an effective strategy for weight loss. (3)

High-fat diets can easily turn into unhealthy diets that lead to high risk of CVD and insulin resistance, and high-fat diets generally have high energy densities. (5) According to the CDC, 1 in 6 children and adolescents is obese and obesity affects 12.7 million children and adolescents between the ages of 2-19 years old. There is a 75% predicted increase in obesity by 2018. Children who are overweight and obese are more likely to become overweight and obese as adults. (CDC) Studies have shown that for every hour of exercise a day, risk for obesity is decreased by 10%. (2) The measure of physical fitness in children and adolescents can display health as well as predict future health outcomes as an adult. (7)

The purpose of this study was to evaluate if diet and BMI of children affected physical fitness levels by using data from the NHANES National Youth Fitness Survey. Energy density and total fat in the diet, as well as the BMI of the participants, were the variables used to assess performance on three important physical fitness categories, measured by the outcomes of four different physical fitness tests. The objective was to determine if BMI, energy density, and fat intake was significantly associated with physical fitness levels, and what this could mean as an outcome.


Data Source & Inclusion Criteria

The National Health and Nutrition Examination Survey (NHANES) is a cross-sectional survey that assesses the health and nutritional status of children and adults in the US. This experiment used the NHANES National Youth Fitness Survey (NNYFS). The NNYS is a one-year, cross-sectional survey conducted by the National Center for Health Statistics in 2012. For the purpose of analysis, this was the main source of physical fitness data. It had the purpose of gathering nationally representative data that represented physical activity and fitness levels, as well as provided an evaluation of health and fitness of children and adolescents ages 3-15. Data was collected through fitness tests and interviews. The nutritional component of data in the NHANES comes from What We Eat In America (WWEIA), gathered through dietary recall from each of the participants.

This analysis included a study sample of all children and adolescents between the ages of 3-15, who participated in the 2012 NHANES National Youth Fitness Survey. However, many children between >6 years met the exclusion criteria and did not participate the physical fitness tests used in this study to evaluate fitness levels. This resulted in a final n of 1,224 participants between the ages of 6-15.

Outcome Measures

The outcome measures in this study included three categories of physical fitness. Physical fitness was evaluated through fitness tests as part of the NNYS. Participants 6-15 years old participated in fitness tests (summer 2012), which evaluated the health of each age group. The NNYFS contains examination data that evaluates body measures, cardiorespiratory endurance, cardiovascular fitness, lower body muscle strength, muscle strength, and gross motor development. For this analysis, physical fitness was measured using the following categories: cardiorespiratory endurance, core muscle strength, and upper body muscle strength.

Cardiorespiratory endurance was measured by examining fitness test results of heart rate at the end of the test (bpm) and maximal endurance time (in seconds). Core muscle strength was determined by the number of seconds plank position was held (in seconds). Upper body strength was evaluated by the number of correctly completed pull-ups the participant could do. Each exercise was assessed in regards to BMI, energy density, and total fat.

Demographic Characteristics and Potential Confounding Variables

In order to assess if physical fitness was affected, variables of BMI, energy density (kcal), and total fat (gm) were used. The NHANES gathered data of total nutrient intakes from dietary interviews given by well-trained professionals. The dietary intake data can be used to estimate the types and amounts of food (as well as beverages) consumed throughout the past 24-hours. In the NHANES, body mass index (BMI) was calculated as weight in kilograms divided by height in meters squared (rounded to one decimal place). In order to analyze BMI as a categorical variable (BMI Category), sex-specific BMI quartiles were created from body mass index data and cutoff criteria from the CDC’s sex-specific 2000 BMI-for-age growth charts. BMI category provided four quartiles: 1) Underweight, 2) Normal weight, 3) Overweight, and 4) Obese.

Energy density and total fat were variables used to measure diet of children and adolescents. Dietary intake for energy density and total fat was measured using 24-hour recalls. To account for confounding factors, which occur when the outcome is influenced by a third factor, data from the NHANES regarding age, gender, race and income were used as covariates and all models run were adjusted according to this. What was looked at was whether energy, total fat, and BMI were significantly (inversely) associated with a decrease in physical fitness of children and adolescents.

Statistical Measures Used

Data from the NHANES was analyzed using SAS University Edition (SAS Institute, Cary, NC). To examine if there was a significant association of physical fitness levels with BMI and energy density / total fat intake, the PROC REG procedure was used. PROC REG procedure was used to analyze significance, if any, in upper body muscle strength (pull-ups), core muscle strength (plank), and cardiorespiratory endurance (heart rate, maximal endurance time). These models were adjusted for age in years at exam, race, and gender, and significance was determined with a value of p<0.05. BMI Category was analyzed using the GLM procedure to predict an outcome based on a categorical variable. Graphical data shown below is the performance outcomes based on the data from results of the GLM procedure of BMI category and the specific physical fitness exercises.


The data obtained from this study indicates that there was a significant inverse relationship observed between diet / BMI and various aspects of physical fitness of children and adolescents. There was a significant negative association of energy density in pull-ups (p=0.0458) and heart rate at the end of test (p=0.0195). Total fat intake had a significant inverse affect on heart rate (p=0.0404).

BMI was the most significant factor in affecting physical fitness. Children who are overweight/obese have less upper body strength than non-obese children. The mean number of pull-ups was approximately 5. Children who are obese completed on average almost 4 less pull-ups than children who are of normal weight (see figure 1).

Figure 1.

Source: Julia Wood

Children who are overweight/obese exhibit lower levels of cardiorespiratory endurance than normal weight children. Maximal endurance time was measured in seconds and measures the amount of time the actual exercise test takes (does not include warm up or recovery). The mean maximal endurance time was 650 seconds. Children who were overweight/obese were not able to perform the exercise test as long as those of normal weight. Overweight children lasted about 632 seconds, while obese children only lasted about 551 seconds, compared to normal weight children who could last approximately 632 seconds.

Children with a higher BMI have a lower level of cardiorespiratory endurance. The mean heart rate at the end of the test was 220 beats per minute (bpm). A non-obese child of normal weight had a heart rate of 249 bpm, while an overweight child had a heart rate of 208 bpm and an obese child had a heart rate of 209 bpm.

Children with a higher BMI display lower levels of core muscle strength. The plank is an exercise that assesses muscular endurance and core strength around the trunk and pelvis (NNYFS). Children with a normal weight had a greater ability to hold the plank position. Almost 35 seconds longer than obese children and almost 15 seconds longer than children who are overweight (see Figure 2).

Figure 2.

Source: Julia Wood

Strengths and Limitations

 In light of the results from this analysis, it is important to note the strengths as well as limitations. Strengths of using the NNYFS include the fact that it is a cross-sectional study that represents physical fitness levels and health of US children and adolescents as a whole. This means that the results can be applied to the entire population of US children and adolescents. Results show that there is a prevalence of low physical fitness levels in children and adolescents who have high BMI and an increased intake of high-fat/energy dense diets. From this analysis, the simple promotion of increased physical activity as well has healthy diets can be put out into the public in hopes of slowing the obesity epidemic and better health in children.

There are some weaknesses to this research. Diet factors of energy density and total fat were used in this study. Data was acquired for these two factors by dietary recall, so there is a possibility of recall bias. Also, the NHANES National Youth Fitness survey is of a cross-sectional survey design, so although analysis can point out prevalence stemming from results, it cannot determine causality. This study also uses two physical fitness tests that somewhat depend on weight/body mass. Pull-ups as well as plank exercises may be subject to influence based on body weight, which could skew results.


Our findings from this study indicate that a child or adolescent’s BMI and diet affect his or her performance on physical fitness tests. Children and adolescents who are overweight or obese (85th-95th percentile or >95th percentile) are seen to have lower levels of cardiorespiratory endurance, upper body muscular strength, and core muscle strength. High BMI was seen to negatively affect physical fitness the most and was more significant than any other factor (p<.001).

There is a significant inverse association between energy dense / high-fat diets and various aspects of cardiorespiratory endurance and upper body strength. Physical fitness is a marker of health and can predict health as an adult. Regular physical activity of at least 60 minutes a day for children and adolescents promotes health and fitness and may help to prevent obesity. Strategies promoting healthy eating may also slow the obesity epidemic.


  1. Ortega, F. B., Ruiz, J. R., Castillo, M. J., & Sjöström, M. (2008). Physical fitness in childhood and adolescence: a powerful marker of health. International journal of obesity, 32(1), 1-11.
  2. Ebbeling, C. B., Pawlak, D. B., & Ludwig, D. S. (2002). Childhood obesity: public-health crisis, common sense cure. The lancet, 360(9331), 473-482.
  3. Ello-Martin, J. A., Roe, L. S., Ledikwe, J. H., Beach, A. M., & Rolls, B. J. (2007). Dietary energy density in the treatment of obesity: a year-long trial comparing 2 weight-loss diets. The American journal of clinical nutrition, 85(6), 1465-1477.
  4. Janssen, I., & LeBlanc, A. G. (2010). Systematic review of the health benefits of physical activity and fitness in school-aged children and youth. International journal of behavioral nutrition and physical activity, 7(1), 1.
  5. Guldstrand, M. C., & Simberg, C. L. (2007). High-fat diets: healthy or unhealthy?. Clinical Science, 113(10), 397-399.
  6. Schrauwen, P., & Westerterp, K. R. (2000). The role of high-fat diets and physical activity in the regulation of body weight. British Journal of Nutrition, 84(04), 417-427.
  7. Harper, M. G. (2006). Childhood obesity: strategies for prevention. Family & community health, 29(4), 288-298.

Julia Wood is a senior at Fairfield University in Connecticut where she is preparing to graduate in May 2017 with a degree in Biology and minor in Health Studies. Julia was a 4-year member of the Fairfield women’s D1 cross-country team.

An Overview of the Total Body Conditioning Plan (TBC4)

Here is an inside look at part of a training session from the 4-Week Total Body Conditioning Plan (TBC4). For more of an overall review of the 28-day plan please look here. The TBC4 Plan begins with an assessment and offers short, high-quality strength training options, HIT cardio sessions and nutritional strategies over the course of four-weeks. The TBC4 Plan focuses on changing ones mindset when it comes to exercise and diet.

“Failure is not fatal, but failure to change might be”  John Wooden, former UCLA Basketball Coach

Fitness Assessment

Making the commitment to exercise regularly while focusing on specific diet strategies are two important steps. The basic concept is to use the plan as a template to bolster that commitment and hopefully “ingrain the habits into your brain.” There are 6-steps to follow over the course of the 4-week plan and five of those steps have specific game plans. Each game plan needs to be incorporated into your life-style in order to be successful. The 6-steps talk about the importance of changing mindset, performing an assessment, adding in more daily movement, getting stronger and leaner and finally, the value of getting more sleep. By the time you complete your 28-day plan, you’ll improve not only your health and fitness, but more importantly, exercise will develop into a habit.

Strength Days (3x/week, <30:00 sessions)

Focus on primary movements including the Squat, Deadlift, Loaded Carry, Lunge, PushPull and Trunk Rotational exercises. The key takeaway here is to master these basic movements before increasing any type of volume. Build up to completing 2-4 sets of each exercise using a load that enables you to get 8-20 repetitions per set. If you end up working for time instead of reps, aim for 30-60 seconds of work per set and perform the exercises in a circuit fashion for about 30:00. The goal is three times a week and if you have a long history of working out, you have the option of progressing to every other day. If you’re new to the game, try only 1-2 circuits, 1-2 days a week and add in plenty of recovery between bouts of exercise. The volume of work (sets x reps x load) will depend on your ability and training history.

Cardio Days (3x/week, 15:00 sessions)

Focus on short, challenging, high-intensity interval training (HIIT) when it comes time for cardio workouts and these can be done on a bike, elliptical, treadmill, swimming, on a rowing machine or running. According to Len Kravitz, a researcher at the University of New Mexico in Albuquerque, “HIIT adds up to 15 percent more calories to the total calories expended.” That means if you’ve worked off 550 calories doing HIIT, you can reasonably expect to burn at least another 83 calories post-exercise. The HIIT sessions should include alternating formats using the following two protocols. One option, is to use a 4:00 warm-up followed by interval work using a 1:2 work to rest ratio (i.e. 30-seconds of maximum effort, 1:00 lower intensity) x 5 rounds, then a cool-down for 4:00. The second option, includes a 4:00 warm-up followed by a 30-20-10 protocol. This means 30-seconds of easy work followed by 20-seconds of moderate intensity work and then 10-seconds of maximum effort for a total of one-minute. Repeat this for 7 rounds followed by a 4:00 cool-down. Both of the workout protocols should take you about 15:00. The exercise intensity will depend on your ability and training history. The TBC4 Plan recommendation is to wear a heart rate monitor during workouts especially if you’re new to exercise.

Nutritional Strategy (8 Diet Pillars)

The TBC4 offers 8 Diet Strategies to follow during your time spent on the plan. These include: Diet Strategy #1 – Drink more water first thing in the morning. Diet Strategy #2 – Never skip breakfast. Diet Strategy #3 – Don’t drink your calories. Diet Strategy #4– Be aware of processed foods. Diet Strategy #5 – Decrease your added sugar and salt intake. Diet Strategy #6 – Be aware of portion distortion. Diet Strategy #7 – Eat more fruits and vegetables. Diet Strategy #8 – Decrease your calories prior to bedtime. For an in-depth look of each please read here.

Game Plan: Follow the 8 Diet Strategies each day. Focus on reducing added sugar. A goal for women is <100 calories (25 grams) a day. A goal for men is <150 calories (38 grams) a day. Increase the amount of daily fiber. You can use the exact same number in terms of daily gram that is recommended for added sugar, as your goal.

The following is an example of part of a training session for someone other than a novice.

(Part of) Dynamic Warm-up

Mountain Climber (perform in “slow motion”) As movement competency improves the individual would progress to a faster pace for repetitions or time.

Weighted Step-Ups

Inverted Row


Hammer Curl/Squat/Press

Hanging Abdominals

Strengthen Your Abs and More with this Four Exercise Core Series

Walk into any gym across the country or look no further than Facebook or Instagram and you’ll see it all when it comes to exercise and various movement patterns especially body weight and core exercises. The questions you should be asking yourself though when looking at all these videos or pictures, is it coming from a credible source? is it going to help me improve my performance? and more importantly, will trying it actually hurt me?

Rather than trying to focus specifically on abdominal or core exercise, think about performing full-body type movements that will engage your core. That can be everything from squats, to overhead pressing movements, to Olympic-style lifts to loaded carries. Because guess what, your core is constantly being utilized during such movements and the reason why they are so efficient is because the whole body is performing in concert and functioning as this kinetic chain, from your head to your toes, rather than segments trying to work individually and we all know training our body that way is not optimal.

There may be times, however, when you would want to focus more on this group of muscles that make up your core for circuit-training programs, dynamic warm-ups, a plank-challenge or when your trying to recover from an injury. The following exercises that make up my core series, in my opinion, are some of the safest, more productive, movements you can do, unless you have been told by your physician or physical therapist that a specific movement is contraindicated. One of the first things that you should notice, in all three videos and one photo, is the position of the spine. The spine is kept relatively “straight” throughout the movements; there is not a lot of spinal flexion as seen with traditional sit-ups. When rotation is brought into play, the lower (lumbar) spine has minimal movement and the pelvis is held in a neutral position.

These movements can be performed for a desired amount of repetition or for time. As your fitness level improves you could progress and complete the full core series back-to-back in a circuit fashion.

Core Series 1: Birddog progression. Make sure your wrist is directly under your shoulder and your knee is positioned below your hip before you start. Keep the hips level throughout while performing the movement slowly. Pretend your balancing a cup of hot coffee on your backside. If this is a new movement for you – start with birddog – simply hold the extended arm/leg for reps or time.

Core Series 2: Russian Twists. The key take away here is to stabilize the hips and get the rotation from the mid-back (thoracic spine) not the low back (lumbar spine). If this is a new movement for you take away the medicine ball. When you’re able to hit your desired reps or time then progress to using the med ball.

Core Series 3: Roll-outs. Start with a short range of motion then slowly increase the distance you rollout. Again, work for desired reps or make it time based (i.e. 30-seconds of work).

Core Series 4: Plank. Position hands directly below shoulders. Think of your body as one straight line from the ankle through the knees/hips/shoulders through the ears. Look slightly beyond your finger tips. Engage your core, contract the buttock and thigh muscles. Beware of your neck, avoid excessive flexion or extension. There are many progressions you can eventually add to this position. Build up to holding the plank position for 2:00 though before getting fancy and trying a weighted vest or bringing in any shoulder flexion or hip extension.


Making Small Changes Can be Key for Improving Health and Fitness

Source: http:/marc.ucla.edu

The cumulative effect of small changes are key to improving both your health and fitness level. Most people are looking for the home run or the secret “ingredient” or new diet when it comes to trying lose weight or improve their fitness level. As an alternative approach, begin to develop new habits with just a few small changes throughout your day that can be added to your workout and diet. When this is done consistently for about 2-4 weeks you will start to notice changes in the way you look and feel.

“Setting the right goals is an important first step. Most people trying to lose weight focus on just that one goal: weight loss. However, the most productive areas to focus on are the dietary and physical activity changes that will lead to long-term weight change. Successful weight managers are those who select two or three goals at a time that are manageable.”

– National Heart, Lung and Blood Institute

Here are a few examples that you could start with.


-Drink more water first thing in the morning
-Make sure you eat breakfast
-Try squeezing in some activity like walking/hiking or a specific exercise (i.e. plank/bridge combo)

-Workout at lunch time if your able and if not, go for a 20-minute walk
-Add more protein to your lunch and avoid bread and fried foods
-Stand more at work rather than sitting for 6-8 hrs (make a standing work station)

-Make dinner your smallest meal of the day
-No eating within 3-4 hours of going to bed
-Cut down on your TV and screen time especially before you go to sleep

Finally, throughout the Morning/Afternoon/Evening watch your “added” sugar intake – this one simple tip will pay back big dividends in no time! If you’re a female work on consuming 100 calories a day of added sugar (25 grams/day) and if you’re a male work on taking in 150 calories a day (38 grams/day). Another tip, eat the same number of grams of fiber/day that is mentioned for added sugar.

If you can add a few of these changes in with your weekly strength and cardio routine, over the course of the next month, it will give you that boost that you have been looking for especially during the remaining winter months!

The Valentines Day Plank Challenge

Y1078190_10201784686800718_635469599_nou have exchanged your cards and maybe some dark chocolate for Valentines Day. What next? For the next 30-days you can try the Valentines Day Plank Challenge. Do it by yourself, with that special someone or in a group…but do it.

If you have never done a prone plank before then try to see if you can hold the position for 20-30 seconds and move forward from there. I started with a minute today and will try adding 5 seconds a day for the next 30-days but you should progress depending on your own ability. Give it a try. Take your Smartphone out, lay it on the floor, set the stopwatch and go. Remember to fully engage your body and be mindful of key areas like your abs, quads and glutes. Pull your navel in towards your spine and maintain throughout, contract your quads and glutes throughout. Keep your gaze slightly beyond your fingertips.

You can start with your arms bent or straight – it’s your call. If they are straight, remember to keep your shoulder blades protracted throughout the entire set. Think about driving your upper back towards the ceiling. Focus on controlling your breathing, feel strong, rock-solid, while doing the movement each day for the next 30 days. Look forward to doing it and turn the exercise into meditative experience each day. You can hold it for a set amount of time each day (like 30 seconds or 1:00) or you can try what I’m doing and increase the duration each time you get down into your prone plank position. You can also increase the intensity over time by trying different progressions: lift one leg, one arm, one arm/leg, do it with hands on a medicine ball, feet on stability ball, you get the picture. Good luck and get ready to build some strength and endurance! Let me know how it goes.

A Complete Workout: Stadium Stairs and SUP

photo-47A great full body workout that can be done that targets just about every muscle in your body is a combination workout that includes both stadium stair walking/running and stand up paddle board (SUP).  Your mission if you choose to accept it:  In the morning hit the local high school or college stadium for a high intensity stadium stair run or if you are looking for something less intense try walking the stairs instead.  You can have a goal of a specific amount of stairs to climb (i.e. 500 – 1,000 steps) or you can work for time (i.e. 20/40/60 minutes).  Alternating between walking and running might also be the ticket that works well for you.  To make this superior workout even better try adding some abdominal work, push-ups or dips between sets of stairs.  If you’re looking for a challenging combo exercise that hits the abs and upper body, try prone stabilization (i.e. plank) with knee ups followed by pushups.  A typical set would look like this.  Walk or run up a set of stairs then walk down slowly.  If, for example, it takes you 20 seconds to run up the stairs take 40 seconds to walk down slowly to recover.  Once you are down get set and perform prone stabilization or plank (on forearms or with arms fully extended) – hold the position and then take your right knee forward and touch your right elbow and repeat on the opposite side.  Follow this with a pushup or add a pushup progression like T-pushups.  This would equal one repetition.  Complete three repetitions and then try another stair walk or run.

Following the stadium stair workout you’re now ready for part two, SUP.  If you are looking for a more challenging workout, then you can head to the beach and if not, head to a pond or bay area where you have more tranquil water. Try to alternate your time spent paddling on the water between standing and kneeling.  The combination of both the stair workout and the SUP will literally work just about every one of the more than 600 muscles in your body.  If you’re looking to increase the intensity a bit try a few of the plank/pushups off your SUP and enjoy your beautiful surroundings!