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Dear Mark: Seaweed Supplements, BMI and Mortality, and Sleep Versus Exercise

In today’s Dear Mark [1] I discuss my favorite seaweed supplement, kelp granules, which aren’t really a supplement in the classic sense, but more of a food that you can treat as a supplement [2]. Next, I give my thoughts on the latest study to suggest that an overweight BMI confers the lowest mortality risk in people. Finally, I handle a question from a parent currently trying to juggle sleep with exercise who wonders which to choose. It’s a tough question, to be sure, but I give my best attempt at a helpful, realistic answer.

Let’s get to it:

Hi Mark, Is there any one special brand of seaweed supplement that you would recommend?



Usually, I eat seaweed [3], rather than take seaweed supplements. I’m a big fan of seaweed salads from good sushi spots. They’re generally made with sesame oil, a touch of sugar, and rice vinegar, so they’re pretty Primal. I also like to drop a ribbon or two of kelp (kombu) into my bone broths [4] an hour before I strain them. And roasted nori sheets [5] are good as edible wrappers or roasted with a light dusting of olive oil [6] and sea salt [7].

If you’re looking for brands, Maine Coast Sea Vegetables is a reputable one. They harvest their sea vegetables in the North Atlantic, regularly test their products [8] for heavy metal contamination, and provide nutritional information for everything. I keep a few containers of their kelp granules [9] (the seaweed highest in iodine [10], with a quarter teaspoon offering 20 times the RDA), and these could easily be used as a supplement. Sprinkle them on food, into water, broth, tea, or even just the palm of your hand. They lend a crunchy, briny flavor. Very tasty.

What do you think about this latest study?

CDC Researchers Find Lower Mortality Rates Among Overweight People [11]

Should we be keeping some fat on ourselves vs getting down to less than 10% body fat OR would you say that 99% of these unhealthy thin people simply lacked the proper lean body mass and organ reserve that chubby people might have on them? I’d love you to share your thoughts with the MDA community!



This isn’t a new idea. For many years, studies have shown that “overweight” people (in terms of BMI) generally live longer than normal or underweight people. In fact, this latest study [12] is a meta-analysis of all of those other studies. Here are a few thoughts:

As you guessed, part of it probably comes down to lean body mass, which BMI on its own can’t really track. In elderly Asians [13], BMI had no correlation to mortality risk, while more lean mass was linked to a lower risk. More lean mass means more mobility and strength, more organ reserve [14], and a greater ability to take care of oneself (shop for groceries, drive a car, get up out of bed, carry things, and generally be able to function day-to-day).

What about waist circumference or visceral fat versus subcutaneous fat, neither of which the meta-analysis examined? Studies that factor in waist circumference – a pretty good indicator of body fatness – show that smaller waists are healthier. In fact, a recent study [15] that compared the utility of BMI and waist circumference in predicting mortality determined that while BMI is useful, waist circumference is more predictive. Visceral fat is also an independent predictor of mortality risk [16]. If your BMI is higher because of squishy subcutaneous body fat, you’ll probably be healthier and die later than the guy with the same BMI because of hard intra-abdominal fat.

Illness often reduces bodyweight, too. Think about cancer, the treatments for which tend to kill appetite and reduce BMI. If you’re on the lower end of the BMI because you’re battling cancer, your mortality risk is going to be higher. Furthermore, heavier patients usually recover better from surgical procedures, like coronary bypasses [17]. And in one study [18] where BMIs between 22 and 26 were associated with the lowest mortality for the general population (but slightly higher for the elderly), excluding smokers and cancer patients pushed the low-mortality range “leftward” to 20. Another study [19] showed that among men aged 65-93, those who lost weight – even if it was body fat – had a higher mortality risk. Gaining body fat was also linked to increased mortality, but the safest move was remaining weight stable.

What about morbidity – quality of life as one ages? Research [20] indicates that those with an overweight BMI do live longer, but with a greater incidence of arthritis, diabetes, and general physical disability. Personally, I’m more concerned with improving and maintaining a high quality of life than I am with living past 100. I’d rather die younger and disease-free [21] than older and kept alive with a plethora of medications and interventions. Live long and drop dead [22], I say.

There’s definitely something to having some meat on your bones. I’d hazard a guess that a mix of lean muscle and some subcutaneous fat layered on top of dense bones is the best mix for longevity and health as we age, but let’s not get carried away. All else being equal, on an individual level, being not-fat (not necessarily six pack-lean), active, fit [23], strong, and mobile [24] are still the surest paths to health and happiness. This study doesn’t change that.

Dear Mark,

Thank you so much for all you do to inspire and teach so many people.

I appreciate the wisdom of the PB very much. However, lately my husband and I have been struggling to get both sufficient quality sleep AND reasonable exercise. We have a 6-month-old and a 3-year-old, and we are up at least twice and sometimes more each night. (Some people call this “nighttime parenting,” some people call it “totally sucks”…we are just trying to deal.) We both work outside the home. My husband tries to exercise in the early morning and I aim for after the kids are asleep, but both of us struggle to actually get it done, often opting for sleep instead. We do our best to make weekend family time active, but those playtimes, while fun, don’t feel sufficient. Please trust me when I say there isn’t time on weeknights between the time we get home and the time we put the kids to bed to take a significant family walk or otherwise mesh exercise with family time.

For situations where one really has to choose between sleep or exercise, which would you say is more important? Should we choose sleep 50% of the time and exercise the other 50%? Just focus on proper nutrition?

Thanks so much for any thoughts you can share.



Sleep is more important than exercise, if you have to choose. Poor sleep makes you insulin resistant [25], thus countering the insulin-sensitizing effect exercise normally has on muscle. Poor sleep increases oxidative stress and inflammation [26], essentially acting as another stressor [27] on top of exercise. Sleep deprivation also worsens your posture [28], which will negatively affect your ability to safely perform exercises, particularly full body compound movements (like squats and deadlifts). A poor night’s sleep will even impair your performance [29] when you do decide to lift heavy weights, making your workouts less effective. Exercise will often feel harder without enough sleep [30], even if you’re not actually working any harder.

“Reasonable exercise” is relative to your situation. If you’re not getting enough sleep, the level of exercise you’re managing to get may in fact be reasonable. You just have to accept that, and realize that trying to circumvent this will only make your fitness and health even worse.

When you do exercise, I have some tips:

Exercising like this won’t really heap a lot of stress [36] onto your already stressed body, but it will keep you mobile, keep you strong, and keep you pretty fit. What’s more is that this is probably how Grok [37] spent his days, with bits of activity peppered throughout.

You might want to consider co-sleeping, if it works for you. I know the practice gets a bad rap from most pediatricians and Western society at large, but co-sleeping with your children/infants is the ancestral parenting norm, and it can really reduce the stress of having to wake up during the night. You’ll still have to wake up, but you won’t have to get up and walk to another room to tend to the little ones. You can breastfeed in bed, or even while dozing. In case you’re worried about being the weird parents, even in the US, where co-sleeping is officially frowned upon and most parents deny practicing it, research suggests [38] that it happens far more frequently than reported. They may say they don’t co-sleep while in reality they’re sharing beds several days a week. Co-sleeping doesn’t have to mean bed-sharing, either; you can have the crib or bed right next to yours. Just a thought.

That’s it for today, guys. Thanks for reading.