I was doing a bit of TV surfing last weekend and came across a PBS special called Master Your Metabolism. The talk was being given by Jillian Michaels, the famous trainer from The Biggest Loser show and author of a recent book called Master Your Metabolism. It had just started so I decided to watch the whole thing. I then went to the book store and looked through her book. Here are my thoughts on the information presented on PBS and in her book.

First, I would give an overall rating of 3.5 stars (out of a possible five) for the book/presentation. So, overall, I think the information is pretty good. Here is the list of things I liked:

  • Hormones are very important for health and weight management
  • Foods and exercise can modify hormone levels making it easier or harder to be healthy and maintain a healthy weight
  • Eat real food
  • Avoid processed foods
  • Eat more organically produced foods
  • Minimize your exposure to chemicals from personal care products and other commonly used products
  • Minimize carb intake at night so that there is a better growth hormone output while you sleep
  • Eat a good amount of protein, about 30% of your diet
  • Drinking alcoholic beverages is very counterproductive for weight loss

Okay, good so far. However, things start to fall apart.

The first problem is the lack of discussion of the psychological and social aspects of eating behavior. As Matt and I stress in SPEED, it is not just about exercise or diet and how they affect our metabolism/hormones. Her focus on the nutritional and exercise components makes this book incomplete. To be fair, most weight loss books take this same approach and look at only a single or small number of potential variables. As you know from our book, we feel that this is a major reason for the poor success rates.

There were a number of statements that were a bit bombastic. For instance, she stated that “genetics does not contribute to aging or disease” and “hormones do not naturally decrease with age” really!? I believe that both of these statements are completely false. The following are more appropriate statements; “Genetics play a part in the development of disease but lifestyle factors, such as diet, exercise, etc. can modify how the genetics are expressed” and “Hormones do decline during aging, but a good amount of that decline can be reversed by following certain lifestyle habits”. Both of the latter statements are clearly not as enticing and do not have the same WOW factor but they are much more in-line with our current knowledge of these factors.

She also said that high sodium would cause an increase in cortisol levels as well as an increase in blood sugar and make you hold onto water, i.e., make you feel bloated. First thing, there is only a small percentage of the population that is salt sensitive. This means only a small percentage of people may have a negative reaction to high salt intakes, such as an increase in blood pressure. Additionally, the reaction to higher salt intakes also depends on the intake of other minerals such as potassium and magnesium. If these are also high then it is possible that the high salt intake will not have a negative effect. Anyway, when it comes to salt intake and cortisol the evidence for this connection is weak. Like the blood pressure affect, it seems that only salt sensitive individuals may have a change in increase in cortisol levels with a high sodium intake. However, the affect in one study was very small. (Kerstens et al) Another connection I found regarding salt and adrenal function is something called adrenal fatigue. (Wilson) This condition is caused from low adrenal function (the adrenal cortex produces cortisol) resulting in many common symptoms; fatigue, poor exercise tolerance, poor sleep patterns, sugar cravings and so on. People with this condition are recommended to make sure they get enough salt in their diet. Overall, I would not worry too much about salt intake as long as you are getting plenty of real, whole foods (i.e., eggs, beef, salmon, veggies, avocados, nuts, etc.)  in your diet.

Related to the issue of cortisol and nutrition is the cortisol and exercise connection. It seems that high amounts of exercise, particularly a combination of high intensity and high duration, and coupled with unfit individuals, will cause a strong stress reaction and increase cortisol levels. Chronically elevated cortisol levels are bad for our weight and our overall well-being. Therefore, why would Jillian and the other trainers on The Biggest Loser show use this type of training? If Jillian is so concerned with high cortisol levels why would she do this to her clients? It would seem counterproductive to health. However, from the results on the show, it does not seem to inhibit weight loss. This is because there is a big caloric deficit. Certainly this strategy, in the short term, will result in weight loss, but is it good for long-term results and health? The exercise and stress/cortisol literature seems to point to shorter duration (less than 60 minutes) and relatively high intensity as the more appropriate exercise recommendations for positive hormone changes, particularly during energy restriction (i.e., reduced calorie intake).

She also states that Atkins, South Beach, no carb and no fat diets are fads and should not be followed. She, like many other people, continually refers to low carb eating plans as fads. Low carb eating is not a fad and has an abundance of clinical and epidemiological evidence to support the efficacy and safety of this type of eating style for weight management and health benefits. She also continues to perpetuate the myth that Atkins, South Beach and other low-carb eating plans tell you to eat NO carbs. The low-carb plans recommend you eat lower amount of carbs, often less than 40% of total calorie intake, not zero carb. Usually 10-30% of calories as carbs are the recommendations of many low-carb plans. But, yes, there are ketogenic food plans that do recommend very low carb intakes, 5-10% of calories, but still not zero.

The final thing that she really stressed was to never skip meals and to eat every four hours. This is apparently necessary to keep the metabolism going and to make sure that blood sugar stays at a proper level. Jillian, like many other fitness and nutrition gurus, are very concerned about eating often and not skipping meals. Why? First, eating more often does NOT speed up your metabolism. Second, from her statements about eating frequency, we can assume that she has not read the large body of research on the health benefits of intermittent fasting (eating every other day) (Johnson et al; Varady et al) or the eating frequency literature (Mattson)? Third, why 4 hours between meals? Why not 3.5 hours or 4.5 hours or 4.25 hours? There is no magic to eating every 4 hours. Third, blood sugar regulation is controlled by many mechanisms and eating frequency is just one of them. Overall, the body can go many hours, even days, without eating and maintain a healthy blood sugar level. (Mattson) For example, usually every day the body goes without food for 10 hours, the hours between your last meal and breakfast, and seems to do just fine.

I bring up this information because it bothers me when poorly supported or non-supported recommendations are given by people who should know better. Jillian and other popular exercise and nutrition experts can have a strong influence on the behavior of many people. They should realize their influencing power and make sure that what they are saying is well-supported! For those of you who are aware of Jillian’s information, please keep the information presented here in mind when you are contemplating using her recommendations.



Kerstens, M. et al (2003). Salt loading affects cortisol metabolism in normotensive subjects: relationships with salt sensitivity. J Clinical Endocrinology; 88(9): 4180-4185.

Johnson, J. et al (2006). The effect of health of alternate day calorie restriction: Eating less and more than needed on alternate days prolongs life. Medical Hypotheses; 67: 209-211.

Mattson, M. (2005). Energy intake, meal frequency, and health: a neurobiology perspective. Annu Rev Nutr; 25: 237-260.

Varady, K. & Hellerstein, M. (2007). Alternte-day fasting and chronic disease prevention: a review of human and animal trials. Am J Clin Nutr; 86: 7-13.

Wilson, J. (2001). Adrenal fatigue: the 21st century stress syndrome. Petaluma, CA. Smart Publications.

Jillian Michaels on PBS – useful information?
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