Sunday, March 22, 2009

When to Stretch and Why

Sara Fleming, BA, MS, ISSA CFT

Stretching is generally viewed as beneficial. However, the type and timing of the stretch can have a positive or negative effect on the person doing the stretching depending on their activity. Dynamic stretching before a work out helps muscles warm up and increases their range of motion and elasticity prior to exercise. Static and/or proprio-neuromuscular-facilitation (PNF) stretching after an exercise and/or during the cool-down phase of a work-out can help restore a muscle’s range of motion after repeated contractions, correct a range of motion for correct form during a lift, and may help reduce delayed onset muscle soreness (DOMS).

It has been hypothesized that static stretching immediately prior to athletic competitions requiring power and force may actually diminish performance. (Shrier, 2004) In addition, Shrier hypothesizes that static stretching can cause an anesthetic (pain reducing) effect on injured muscles, increasing the performance of the athlete at the risk of increasing the severity of the injury. Shrier concludes that regular stretching will improve performance, but it should not be done immediately prior to athletic competition. Therefore, it is reasonable to conclude that although stretching plays an important role in general fitness and athletic competition, close attention must be paid to the both the type (dynamic, static, or PNF ) and the timing of stretches used.

Decreased range of motion (ROM), which can result from a number of factors both within and beyond an individual’s ability to change, can lead to injury and affect an individual’s performance and overall fitness. However, one must keep in mind that achieving a broad range of motion without complementary strength, disallows the muscles to properly support the new joint position which invites injury as well. Therefore flexibility and strength training must be done jointly. In addition to stretching, flexibility can also be achieved through a well-balanced weight training program where agonist/antagonist muscle groups are trained equally with light weight through a full range of motion.

It is important that in the pursuit of increased range of motion, one does not aggressively stretch to the point of causing muscle or tendon damage or diminish the ability of the individual to perform optimally. Unless a particular sport demands extreme flexibility such as gymnastics, ballet, or martial arts, a standardized range of motion that can be assessed by a qualified coach or trainer is an adequate objective for most fitness programs.

Proprio-Neuromuscular-Facilitation Stretching
This is a big confusing word to mean something very simple. We can take advantage of our nervous system to enhance our flexibility by selectively contracting and relaxing muscles. These are the mechanisms by which Yoga stretching works and the reason that dynamic stretching works so well. The more complex methods are best left to a physical therapist, but I will explain two methods here that are easily used and can greatly enhance your flexibility at home or in the gym.

Contract Relax Method
Inside your muscles are specialized receptors called proprioreceptors which are your safeguards against severe muscular injury. When there are sudden changes in muscular tension, these inhibit your muscles from stretching any further. One of these receptors is called the muscle spindle. It is actually a specialized muscle fiber within the muscle. In order to reset the muscle spindle and allow the muscle to stretch, you simply have to contract the muscle and then allow it to relax. Therefore this method is called the contract relax method.

To perform this stretch, you contract your muscle against force either actively or isometrically. When you relax the muscle and stretch it out, you should be able to move it through a wider range of motion. For example, try a dumbell Romanian deadlift (stiff-legged deadlift). Basically you are trying to touch your toes while holding weights. In order to stand back up straight, you contract your erector spinae, your gluteal muscles, and your hamstrings. Hold for 6 seconds. As you lower the weights back down to the floor, you will find that you can get much lower because your muscles can stretch a little further this time. If you repeat the exercise 2-3 more times, you will find that your range of motion will increase with each repetition.

Another example is a lying hamstring stretch. I do this by lying flat on my back with one leg up in the air with a towel looped around my foot to pull it up towards me while keeping my leg relatively straight. Using my hamstring muscle, I push my leg back down towards the floor isometrically while holding it in place with the towel. I then relax the muscle and pull my leg towards my head with the towel. After the muscle contraction, I am able to pull my leg more perpendicular to the floor.

Contract Antagonist-Relax Method

Agonist and antagonist are terms used to describe opposing muscle groups. For example, a bicep would be the agonist if the triceps was the antagonist. Similarly, the quadriceps would be the antagonist if the hamstring was the agonist. There is a phenomenon that occurs in our nervous system known as reciprocal innervation. Again, to prevent injury, since these muscle groups work on the same body parts, to contract at the same time would be bad. So, when one contracts, the other MUST relax and lengthen. To take advantage of this phenomenon, known as reciprocal inhibition, we can contract the antagonist of a muscle group we are trying to stretch in order to optimize its ability to lengthen and relax.

A classic example of this method is the Uttanasana pose in yoga which is basically standing straight legged and bending over and touching the ground. The erector spinae and hamstring muscles usually feel rather tight and uncomfortable as you bend over and reach the ground with knees bent. The Uttanasana progression has you relax your knees to relieve the pressure of the stretch and then contract the quadriceps to re-enter the stretch with straight legs. As you do this, you will find that you can get deeper into the pose more comfortably. Let the knees bend again and rest a few seconds and when you are ready, engage the quadriceps once more and straighten out your legs, keeping your hands close to the ground. You will find that you can more comfortably hold the position.

Another version of this stretch is very simply the stretch we all tend to do when getting up in the morning. Arms are up, elbows are bent, back is arched, and then we contract our back muscles and open up the chest. When I try opening my chest by just opening my arms as wide as possible, I can only get so far and my chest and anterior shoulders feel tight. When I contract my back muscles at the same time, my humeral head goes back another inch or two and I do not feel any tightness in my chest or shoulders.

These CR and CA methods of stretching are very similar to the stretching progressions found in yoga, dynamic stretches, plyometrics, and are also very similar to the stretching effect during amortization (the change from concentric to eccentric phase) when weight-lifting or strength training. Its easy to see how correct form and a complete range of motion while weightlifting can enhance or even increase one’s flexibility. Personally, I have found yoga and weight lifting to be synergistic both for increasing strength and flexibility.




References

Hatfield, Frederick C. Fitness: The Complete Guide 8.6.6, ISSA 2004

Shrier, Ian “Does Stretching Improve Performance”, Clin J Sport Med, 14:5, Sept. 2004

Performance Nutrition

Performance Nutrition
Sara Fleming, B.A., M.S., ISSA Certified Fitness Trainer
*Sara is not a licensed or registered dietician

Most of us are exercising for one of two reasons: To get bigger, or to get smaller. Some of us are exercising for both of those reasons, ie increasing our lean body mass while getting rid of the flab. This task can seem quite daunting, but the truth is, changing our body composition takes place mostly in the kitchen and not in the gym. If we overfuel our bodies with too much, poor quality, and/or the wrong kinds of nutrients, we will not be able to reduce our bodyfat stores. Likewise, if we under fuel our bodies with inadequate micro and macro nutrients such as protein, vitamins, and minerals, we risk overtraining* and fail to reach our fitness goals no matter how long and how hard we may work. For that reason, nutrition is every bit as important to your fitness regimen as your exercise prescription. Seeing a registered dietician for a personalized nutrition plan may be as important as seeing your personal trainer for a personalized exercise plan.

Performance nutrition is a tricky subject. We require a delicate balance of the right forms of carbohydrates, proteins, and fats to carry out a number of vital operations. We need to nourish our bodies to get through daily activities, fuel our performance to get the most out of our workouts, repair our muscles and organs, build and replace the right biomolecules such as enzymes and hormones to keep our bodies in balance, and strengthen our tendons and bones. Carbohydrates, proteins, fats, vitamins, minerals, and water are the most important nutrients to consider when coming up with a diet plan to support exercise and every day activities. The confusing part comes when trying to gauge in what form, how much, and in what ratios those nutrients should be consumed.

*overtraining refers to the condition where exercising without adequate nutrition and rest over time causes the body to break down

Macronutrients: Carbohydrates, protein, and fats.

Carbohydrates come in three forms; basically starches, sugars, and fiber. Carbohydrates are used primarily for energy in high intensity exercise, usually the anaerobic pathways such as weightlifting or power sports. They are also required to help fuel the fat burning pathways of low intensity exercise such as long slow distance running or every day activities. In the absence of carbohydrates, the body will burn amino acids instead. That means that with an inadequate diet and/or improper timing of exercise, muscle tissue will actually be broken down and cannibalized as you exercise.

Once carbohydrates are consumed, they cannot be used until they are broken down into their single sugar-forms by a variety of digestive enzymes and absorbed through the wall of the gut. The more processed and pure these carbohydrates are, the more quickly this process takes place. Once the sugars are absorbed into the bloodstream, the pancreas releases insulin to bind the sugar and deliver it to the muscles and organs where it is used as fuel. Small amounts of excess sugar are stored in the liver and muscle cells in long chains called glycogen while larger amounts of sugar can be stored in fat cells as excess bodyfat.

When large amounts of sugar are introduced into the bloodstream, the pancreas produces large spikes in insulin. This insulin immediately routes the sugar to be used for energy and stored as glycogen by our organs and muscles. Only so much sugar can be used for energy and glycogen storage at a time so when there is a large sugar spike, most of this sugar will be routed to the fat cells to be stored as excess bodyfat.

This immediate routing of the sugar to the organs and fat cells immediately drops the amount of blood sugar rather quickly resulting in the sensation of being hungry again, even though a large meal may have just been consumed. As you’ve probably guessed, this is not a good thing. When our bodies get used to having large insulin spikes, our organs may eventually adapt to try and protect themselves from the excess sugar by becoming insulin resistant. Fat cells, however, do not become insulin resistant, which means even more sugar gets stored as excess bodyfat. This means that individuals who are insulin resistant have less energy and a harder time losing weight.

Therefore, it is important that we control the rate at which sugars enter our bloodstream. We can do this both by controlling the volume of carbohydrates we consume and by combining them with other foods that slow down their absorption rate. The absorption rate of carbohydrates relative to pure sugar is known as the glycemic index. Although individual foods have their own glycemic index, this can be altered by combining them with other foods. Not all carbohydrates go through the wall of the gut at the same rate and not all carbohydrates, such as fiber, get absorbed at all. Starchy and sugary foods such as pasta, white rice, white potatoes and candy have a high glycemic index while more fibrous, high protein, or acidic foods such as sweet potatoes, blueberries, brown rice, and oatmeal have a low glycemic index. Combining carbohydrates with fiber, proteins, and acidic foods such as lemon juice and vinegar (think salad dressing) will lower the glycemic index of foods and therefore lower the rate of absorption of carbohydrates into the gut and the release of insulin.

Tip: Add ½ cup dried chopped figs and 1/4 cup wheat germ (remove ¼ cup flour) to your next batch of chocolate chip cookies. It will lower the glycemic index and not change the taste much at all.

Two nutrients that are inextricably linked in the American food industry are protein and carbohydrates. Most people think they get enough protein in their diets because they follow the food pyramid. And that would probably be true if they ate fruits, vegetables, and whole unprocessed grains. But, as a country, we don’t. In the last 100 years, grains have been processed, pulverized into submission, filtered, and bleached until there is only a very fine starch left for us to consume. No fiber, no protein, no vitamins, or mineral are left. These are added back in to this very fine powder as an afterthought. This very fine powder quickly sheds its added “whole-grain-appearance” once eaten and enters the bloodstream almost instantly, spiking the blood sugar levels astronomically. If only the grains were left intact with their fiber and protein to slow things down a bit . . .

Protein is extremely important in our diets, but we rarely treat it as such. It is the fundamental building block of the muscle framework that supports our skeleton, our joints, and our organs. It makes up the millions of biomolecules we need to send signals throughout our bodies, build up defense mechanisms, recognize foreign bodies, fight infections, and create and sustain life. When we engage in exercise, our protein requirements go up as do the requirements of pregnant and lactating women. Maintaining a healthy protein intake is important in maintaining our strength and vitality as we age. It is important that we are cognizant of our protein intake as we should be of all our macronutrient and total nutrient intake.

The average meat-eating American thinks he or she gets plenty of protein in their diet. But this couldn’t be further from the truth. We eat cereal for breakfast, sandwiches for lunch, and usually pasta or rice for dinner with a modest helping of meat on the side. Again, if the cereal and bread we were being served was truly whole-grain in nature, we might be getting more protein than we thought, but for most people that’s not the case. And, for the average person engaging in resistance exercise, its still not enough. According to the Hatfield estimate (Fred Hatfield, Fitness: The Complete Guide), the average person engaging in regular exercise needs a minimum of 0.8 g of protein per lean pound of bodyweight per day. For me, a 135 lb female with 18% bodyfat, that means I need approximately 90 g of protein per day. For someone who engages in regular intense weight-training, that number should go up to 1.0 or 1.5 grams of protein per pound of lean body weight per day. I regularly weight train at least 3 days per week so my protein intake should be closer to 110 or even 165 grams of protein per day.

Let me briefly explain the calculation. I have 18% bodyfat so that means I am 82% lean. I multiply my bodyweight, 135 lbs, by 0.82. That gives me 110.7 lbs. I multiply that by 0.8 (the Dr. Hatfield minimum) to get 88.56 g of protein. I rounded that number up to 90 grams to be even. To calculate 1.0 or 1.5 grams of protein per pound of lean bodyweight, I just multiply 110.7 lbs by either 1.0 or 1.5 grams to get 110 grams or 165 grams.

Here is a look at a sample menu of meals of what I might eat during the course of a day. Because I regularly weight train, I want to try and take in 1 gram of protein per lb of lean bodyweight and make my target protein intake 110 grams of protein per day.


Food Item Calories Carb. (grams) Fiber (grams) Protein (grams) Fat (grams)
½ cup oatmeal 150 24 4 5 2.5
8 oz 1% milk 102 11.7 0 8 2.6
½ cup strawberries 23 5.2 .3 .5 .3
1 scoop whey protein 104 6 0 20 0

1 cup tarragon
chicken salad 180 4 1.2 16 11
½ cup Bubbies
sauerkraut 22 5.5 4 0 0
1 mango 135 37 3.7 1.1 .6

½ cup raisins
and almonds 310 36 3.6 7.25 18.15
7 oz salmon fillet 281 0 0 39.3 12.6
½ sweet potato 117 27.5 3.5 2 .1
1 tbsp hoisin sauce 40 8 0 .5 .75

Total Calories: 1600
Carbohydrates: 165
Protein: 100 grams
Fat: 48.6 grams
Fiber: 20.3 grams

Even though I am getting a substantial amount of protein with each meal and am supplementing with whey protein, I fall short of my target by 10 grams. It’s easy to see how many diets are deficient in protein.

To make sure we get enough protein, we need to look for lean sources of complete protein such as whey, casein, milk, eggs, beef, cheese, chicken, fish, yogurt, cottage cheese, and turkey. Protein is made up of amino acids. There are 20 different amino acids that are combined in different ways to make all of the different proteins in the body. Complete proteins refer to proteins that contain all 20 amino acids. We can mix incomplete protein sources as well to provide all 20 necessary amino acids. Examples of incomplete protein sources are fruits, vegetables, rice, legumes, grains, oats, pasta, some nuts, bread, and sunflower seeds. However, a full complement of all 20 amino acids must be present for protein synthesis to occur.

Tip: Find a pocket protein counter and start looking up the protein content of foods you commonly eat. You will very quickly figure out if you are hitting your daily protein requirement and be able to make adjustments. Try The Pocket Protein Counter by Annette B. Natow, Jo-Ann Heslin (available on Amazon.com)
Lastly, we come to fat. Fat is not a bad nutrient; it is another source of energy just like carbohydrates and it is a necessary building block for many of our body’s structures and biomolecules. Just like carbohydrates, there are good forms and bad forms and we need to be careful as to how much we take in.

Generally speaking, if we are avoiding processed foods, eating lean protein sources and avoiding fried foods and foods covered in mysterious sauces, fats aren’t really going to be a problem. The fats that we get from avocados, salmon, grass-fed beef, nuts, and olive oil are good for us and heart healthy and therefore shouldn’t be avoided.

Although some saturated fats are good, we want to avoid an excess of saturated fats such as cholesterol and look for monounsaturated and polyunsaturated fats. Omega-3 and Omega-6 fats are good for us provided they are in the right proportions. Omega-3 are more often deficient in our diets and are best supplied by natural sources such as cold water fish, flax seeds, or walnuts. Too much Omega-6 can actually be harmful so avoid margarines and vegetable oil spreads that list omega-6 polyunsaturated fatty acids as ingredients.

I would not recommend anything that is artificially “low-fat”, as the fat component is usually made up with sugars or some other carbohydrate or industrial chemical. Ingredients lists with words such as partially hydrogenated vegetable oil or high-fructose corn syrup should be avoided altogether. What is “fat-free” cream anyway?

Tip: (From www.realage.com) Although omega-6 is a healthful fat, getting too much omega-6 without enough omega-3 to balance it out appears to promote a variety of health ills, including insulin resistance, metabolic syndrome, inflammatory processes, and the kind of cell-damaging oxidation that’s associated with aging and damage to cells and DNA. All of this could eventually open the door to serious conditions such as diabetes, heart disease, and cancer.Scientists estimate that our ancestor’s dietary ratio of omega-6 to omega-3 polyunsaturated fatty acids was probably something close to 1/1 or 1/2. Today, the ratio in the typical Western diet is estimated to be anywhere from 20/1 to 30/1. This means that, even if a person is eating a relatively low-fat diet, he or she is probably getting a disproportionately high amount of omega-6 compared to other healthful fats.

Calories and Macronutrient Ratios
Well, we’ve discussed how much protein to take in, but the question that remains is how do we determine how much carbohydrates and fats to take in? And how do we determine overall calories?

Let’s address the calorie question first. For a helpful tool in figuring out how many calories to take in on a daily basis try this free web tool: http://www.freedieting.com/tools/calorie_calculator.htm. It will calculate your daily caloric intake based on your height, weight, daily activity, and weight loss goals. Use the advanced features to add in your body fat percentage to calculate your caloric needs based on lean body mass. This will give you more accurate calculations.

This particular web tool has an extra feature called zig-zag that has been shown by the University of Pennsylvania to be more effective at increasing or maintaining lean body mass while decreasing bodyfat. The idea is that you increase your overall calories on the days you exercise and decrease them on your rest days. The overall average is the same for the week, but it “tricks” your body into gaining, maintaining, or losing those extra pounds by placing those extra calories where needed.

Now that we have a resource to calculate a total number of calories per day (freedieting.com) and a few estimates to calculate your total number of protein grams per day, its time to address that carbohydrate and fat issue. Aside from their roles as building materials, carbohydrates and fats are simply fuel for performance and day to day operations. What doesn’t get used, gets stored as excess bodyfat. What we need to address here is whether to go with a higher fat and lower carbohydrate profile or a lower fat and higher carbohydrate profile to finish our diet profile.

There has been an ongoing discussion in the field of nutrition as of late regarding the low-fat vs low carb diets and which is more optimal for overall health and body composition. Low fat diets have reigned supreme for many decades, but diets such as Atkins, The Zone, South Beach, and the Mediterranean diets with different macronutrient profiles have been making headway in more recent years. Several studies have been published to demonstrate the effectiveness of the calorie restricted low-fat diet, low-carb diet, and low-glycemic load diet. In three of these studies performed on obese adults, it was shown that although all of these diets may be successful for weight loss, the low-carb and low-glycemic load diet had more success at improving blood chemistry and allowing patients with insulin resistance to lose weight. (Ebbeling et al, Shai, et al, Stern, et al)

So, let’s continue to use my sample diet as an example and figure out the rest of this formula using the number of carbohydrate and fat grams that I consumed in one day. We’ll take the total grams of protein and multiply by four (protein has four calories per gram). Freedieting.com gave me 1700 calories to use and because I’m weightinglifting, I want to eat 110 grams of protein per day. That takes away 440 calories right there leaving me with 1260 to divide between carbohydrates and fat.

Fat has nine calories per gram and carbohydrates has four calories per gram. According to the chart I recorded above, I had roughly 50 grams of fat, or 450 calories from fat. I also took in 165 grams of carbohydrates for 660 calories. Combined with the 440 calories from 110 protein grams, that brings me up to 1550 calories total. A little low, but in the range. The American Heart Association wants me to get between 18% and 30% of my calories from fat. That’s going to be between 300 and 510 calories of my 1700 calorie allotment and I’m right up there. Dividing the fat calories by nine gives us the total number of fat grams so that translates to between 33 and 57 grams of fat. I could probably still increase my fat grams a little bit, or add a few more carbohydrates to get those last 110 calories.

How would I make that kind of decision? That’s where journaling comes in. Just as we meticulously record our performance in the gym and what affects our progress, we need to consider our diet as part of that formula, especially if body composition is part of what we are working towards.

Looking at my diet as listed above, I can see that my caloric ratios are roughly 28% fat, 28% protein, 41% carbohydrate. This would be considered a relatively low carb diet, in the range of the Zone or the South Beach Diet. I would be interested not only in tracking my overall caloric intake, but my macronutrient ratios as well over the course of a week or a month and see how they correlate to my performance, my weight gain or loss, and overall sense of well-being. In most cases, the ratio of protein to carbohydrates to fats could definitely be tweaked to achieve an optimal balance for both energy levels and body composition. Also, the nature of the carbohydrates could be changed from more starchy and higher glycemic carbohydrates such as pasta and potatos to lower glycemic and more fibrous carbohydrates such as leafy green vegetables, legumes, and fruits.

When determining one’s “perfect” diet, it is important to remember that we are all unique individuals. Some of us need more carbohydrates or we get to feeling tired and run down. Some of us need more fat and protein in our diets and less starchy carbohydrates or we start to thicken around the middle. In a recent review article in the British Journal of Sports Medicine, it has been observed that female strength athletes rely less on their glycolytic pathways (sugar burning) for strength and power and may in fact, burn more fat than carbohydrates compared to men engaged in similar activities. Therefore, a diet higher in fat and lower in carbohydrate may be beneficial to female strength athletes for both performance and body composition. However, higher amounts of protein were also required. (Volek, et al)

Lastly, although when we do our best to eat whole foods from all natural organic sources, we can’t tell if the fruit is grown in depleted soil or if the animals were given a well-balanced diet so it is always a good idea to supplement our diets with a multivitamin.

In summary:
Prioritize getting your minimum protein intake from lean meats, nuts, seeds, or a whey protein supplement.
Make sure that your carbohydrates are coming primarily from vegetables, fruits, and non-processed whole grains.
If your foods are coming from natural and non-processed sources, don’t worry so much about the fat contained in those foods. Do control portions of added fat such as salad dressings, spreads, and fats used for cooking.
Keep a diet journal so that you can optimize your individual performance and body composition such that making good choices becomes second nature.
Take a daily multi-vitamin.
To optimize your nutrition, work with a registered dietitian to develop a personalized plan specific to your needs, especially if you have a medical condition related to diet such as diabetes or heart disease.

References

Ebbeling CB, Leidig MM, Feldman HA, Lovesky MM, Ludwig DS. “Effects of a low-glycemic load vs low-fat diet in obese young adults: a randomized trial.”
JAMA. 2007 May 16;297(19):2092-102

Hatfield, Frederick C. Fitness: The Complete Guide 8.6.6, ISSA 2004

Johnson, Jo “The Health Benefits of Grass Farming” http://www.americangrassfedbeef.com/grass-fed-natural-beef.asp

Lara-Castro C, Garvey WT. “Diet, insulin resistance, and obesity: zoning in on data for Atkins dieters living in South Beach.” J Clin Endocrinol Metab. 2004 Sep;89(9):4197-205

Netzer, Corrine Encyclopedia of Food Values Dell Publishing, New York, 1992

Shai I, Schwarzfuchs D, Henkin Y, Shahar DR, Witkow S, Greenberg I, Golan R, Fraser D, Bolotin A, Vardi H, Tangi-Rozental O, Zuk-Ramot R, Sarusi B, Brickner D, Schwartz Z, Sheiner E, Marko R, Katorza E, Thiery J, Fiedler GM, Bl├╝her M, Stumvoll M, Stampfer MJ; Dietary Intervention Randomized Controlled Trial (DIRECT) Group.
“Weight loss with a low-carbohydrate, Mediterranean, or low-fat diet.”
N Engl J Med. 2008 Jul 17;359(3):229-41.

Stern L, Iqbal N, Seshadri P, Chicano KL, Daily DA, McGrory J, Williams M, Gracely EJ, Samaha FF.“The effects of low-carbohydrate versus conventional weight loss diets in severely obese adults: one-year follow-up of a randomized trial.”
Ann Intern Med. 2004 May 18;140(10):778-85.

Volek JS, Forsythe CE, Kraemer WJ. “Nutritional aspects of women strength athletes.” Br J Sports Med. 2006 Sep;40(9):742-8
Suggested Reading

Agatston, Arthur The South Beach Diet Rodale Books, New York, 2003

Cordain, Loren The Paleo Diet: Lose Weight and Get Healthy by Eating the Food You Were Designed to Eat Wiley, 2002

Roizen, Michael F. and Mehmet Oz You On a Diet, Free Press, New York 2006

Rolls, Barbara The Volumetrics Eating Plan Harper-Collins, New York, 2005

Sears, Barry Enter the Zone Harper Collins, New York, 1995

Taubes, Gary Good Calories, Bad Calories: Fats, Carbs, and the Controversial Science of Diet and Health Kindle Books, 2007