The Truth About Scientific Claims for Nutrition, Exercise or Weight Loss

I have been blogging here a few months, and absolutely love this place and C25K. I have seen a lot of questions about nutrition and weight loss in conjunction with running, as well as feedback on my own posts asking for more info. And I want to give a little back to a community that has given so much to me. So this will be a slightly unconventional post - or if demand/interest continues, series of posts.

As I begin writing, I realize I want to start with a post about how to sift through conflicting scientific claims, before getting into what I personally have found useful in my own workouts, or with my own food. I believe everyone should have the tools to make these important decisions themselves, while understanding what they really mean. It is a one-time departure into lecture, I promise. If you prefer to skip it, I will understand, but I hope someone, somewhere, finds it useful. To that end, I encourage anyone with doubts to ask a doctor, science teacher or scientist they trust to read this and confirm whether they think it is basically accurate, and to tweak anything they disagree with. The point of this post is to be careful what you believe, so feel free to put my own words to the test. (I welcome any amendments in replies too.)

First, I think I should explain my credentials and lack thereof. I studied molecular biology from a really good school, and once interned as a community health worker. That said, I am not a doctor, nor a nutritionist. I am not a nurse or other medical professional. I am not looking to make money from you or sell anyone anything. I *am* however, pretty well versed in how science "works", and want you to be able to make discerning choices too. Personally, I have (with the help of my doctors, C25K, diet and some really great info on the net) been able to really turn my health around. I have lost 50 pounds since October, and where I used to walk with a cane, I now can run 5K and do so much more than I could have dreamed. I devote a lot of energy to understanding health and fitness as a layperson, and I hope everyone can have the same kind of success.

"Science?" I thought this was about nutrition and weight loss and running! What do I care about nerds in white coats? Well, there is a lot of information out there, especially self-published things on the internet, and I believe it is really important to have to tools to understand if something is likely to be accurate or not. Understanding about science gives you the basic tools for that. This will help you decide if trying a given exercise, diet or following a given running regime is actually likely to give you the results you want.

What is good science? Basically, it's a systematic approach to learning about the world. It should start with an observation. (ex. I know a guy who runs and has low blood pressure.) Then it is followed with a hypothesis, a possible explanation, which can be tested. (Running is associated with low blood pressure.) Then an experiment is designed to DISPROVE the hypothesis. (Testing blood pressure with runners and non-runners who may also have low blood pressure.) If the hypothesis holds up to many tests, with reviews by other experts, it is thought to be accurate and we can start basing our decisions on this new information.

What are the pitfalls? There are many, but here are a few of the biggest.

*) So important it doesn't need a number: Science is only a collection of best guesses that have not been disproven (yet). "Facts" are just ideas that seem accurate so far. Pretty much everything we think of as scientific fact will eventually be shown to be at least partially incorrect. Ex. Newtonian physics: a collection of theories that approximate the world as we experience it in generally simple math. We still use it ALL the time. It calculates gravity, and weight. It powers our bathroom scales. But it turns out that it only works in largish masses at slow speeds. If you approach the speed of light, for example, it all gets messed up. A newer theory came from Einstein with relativistic physics that fixes those problems. (Since then, brainiacs including Steven Hawking found issues with Einstein's work too, and propose alternatives in theoretical physics.) The point is, even things we "know are true" are probably only partially correct. We need to understand that it is always evolving.

1) Correlation is not the same as cause. A classic example: More babies are born 9 months after a power outage than normal. (This is a fact, at least in some places. It is, to be precise, an observation. Statistical analysis of this observation happening over and over have demonstrated a correlation.) Most of us would be comfortable agreeing that power outages themselves do not make babies. It would be incorrect to say it "causes" babies to be born. Instead, the conditions of a power outage are linked to the conditions of more people getting pregnant (you can use your imagination here.) - This distinction is really important. Someone may eat a papaya and lose weight, and if may even be related in some way to eating a papaya, but that does not mean, necessarily, that if you also eat a papaya, you will lose weight. It could be that by eating a papaya, they missed out of a bunch of donuts. Or it could be that papayas themselves cause weight loss. Without more careful analysis, you cannot draw a conclusion.

2) Not all claims can be disproved, and not all experiments are designed properly to do this. Things that may possibly be true but cannot be disproved are pseudoscience. They can be really improbable, or it can be likely to be true. The point is, we don't know. The use of magnets for aligning good energy falls in this category. So does a lot of theoretical physics. (For a great in-depth understanding of psuedoscience, check out It may actually be true, but no peer-reviewed large scale study with a control group has shown that yet, as far as I know. You may choose to believe certain unproven claims, and that doesn't make you silly. I am pretty keen on string theory, but it has some unproven bits still. It just means that you are following a best guess of someone, not a proven theory. (Lots of current science now was once psuedoscience because we lacked the technology to test it properly. It really can be legitimate and accurate, but we also know that many past beliefs (a flat globe, for example) were incorrect - so we have to take it all with a grain of salt.)

3) Experts and scientists have agendas too. Governments tend to be very conservative in their recommendations, to be sure the theories hold up over time and are likely to work for most people. This is perfectly understandable behavior for governments, and I applaud that caution. It does, however, mean that they can be "behind the times" with new discoveries. If there is some new wonderfood that really does cure everything, it may take decades before that shows up in the government food recommendations. On the other end of the spectrum, people trying to develop the new cure-all, are going to lean towards moving quickly to market, without as much time to find out if anyone else can disprove its effectiveness. (And that is just the ETHICAL ones, who actually believe it works. Unethical ones may disregard undesirable data in their own studies and just say it works anyways. So pay close attention to who makes a claim that something is "scientifically proven" to do something. If the only study showing it works is paid for by the manufacturers, understand they may or may not be telling the whole truth.)

4) Human biology is especially hard to test, because humans make difficult test subjects. In most tests, we can't control factors like where they live, how often they eat/smoke/exercise/sleep/talk on the phone/whatever. We can't do things that cause undue trauma or death to identify a causal relationship. To improve the data, we use many, many subjects, randomly assigned, and include a control group - ideally with no one knowing which group they are in. So when looking at medicine, nutrition, health or human biology, we need to be especially careful with the claims that are made. Many times we have to accept a correlation, rather than a cause as "good enough" data.

*** Unfortunately, lots of people rely on "anecdotal evidence" rather than proper experiments. When your neighbor tries a special weight-loss coffee and (honestly) feels fantastic, and kindly suggests you try it too, that is anecdotal evidence. It is possible that this coffee is the best thing since sliced bread, but one person trying something in an uncontrolled environment is not good science. It may work, or it may not. It means you really don't know. The "before and after" pics and customer testimonials (assuming they are all true and honest) also fall in this category. They can be compelling, but try not to get sucked in. Understand that based only on that information, you are trusting pseudoscience - in other words - a hunch or the goodwill of whoever is making the claim. If they provide peer-reviewed studies to back it up, that is a whole different story.

So what is a normal person to do? I mean, I don't have the time or skills to test all this in a lab myself...!

For us mere mortals, we need to decide deliberately what we want to believe, even if people tell us it is a "scientifically proven fact". In our everyday lives, we must usually accept the most prevalent and time-tested theories as "good enough". We assume the theory of gravity is "good enough" to keep our cars on the road, for example. We believe that regular exercise is good for our health.

For things we want to pay close attention to: for example our health as it relates to running, we should rely heavily on trusted sources, understanding their own limitations. If NHS says running is related to weight loss, low blood pressure, and better cardiovascular health, it is reasonable to accept that it probably works, although it may not be the newest information out there. If we take prescribed antibiotics for a bacterial infection, chances are good that it will help us beat the infection.

Then there is the small portions we might be willing to take a calculated risk on. Do I want to try completely cutting out refined sugar and seeing if my skin looks better? Maybe I like my magnet bracelet. Perhaps I want to try more exercise in addition to C25K to increase my weight loss, and go on a special diet. How do I know which is the best? This is where we need to do our own digging to find reliable sources who might be working with newer data. And we need to decide if, should the data prove to be incorrect, that we can risk the likely outcomes. (Cutting out sugar is unlikely to hurt me, regardless of whether my skin changes, so I might take that risk.)

In my next post of the series, I will share some of my own "trusted sources" and some ideas about how to build your own best regimen. (I gave a lot of examples above, and want to clarify that I am not making judgements for or against these examples. Just because something is unproven doesn't mean it is dangerous or won't work - although I hope you will develop some opinions of your own about each instance. Is it safe? Is it likely to work? I will get into personal opinions when I talk about my own personal choices in the next post.)


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38 Replies

  • Great post, thanks! :-) However, are you implying my theory that chewing gum while running regulates breathing is not actually a scientific fact? ;-)

  • Lol. Your hypothesis may actually be quite valid - chewing is rhythmic and so is breathing, why not use one as a "pacemaker" for the other? I recommend testing the theory and letting me know what you find. :)

    Thanks for reading my tome, btw. They will be more entertaining in the future.

  • Just tried that and promptly bit my tongue. ouch!

  • I found this miracle cure to breathing problems in week 4 and not left for a run without a chewing gum since (it's become psychological now, can't run without chewing). Touch wood, no tongue biting so far!!! ;-)

  • It did work despite the tongue biting, I was distracted by the rozzers going for elevenses at a burger van (there were loads of them!). I will deffo try again with the gum :-D good tip

  • Thank you for this blog - I look forward to the next one.

    I've just started a file of training plans etc and anything relevant to improving my running/fitness so I'm going to add this to it. I'm trying to get lots of ideas together and form a plan towards running a marathon next year !

  • Looking forward to the forthcoming blogs Alaiyo, I might learn something!

  • I think your blog will lead to some interesting debates and experiements. keep blogging

  • Very interesting look forward to your next blog :)

  • Great post! This is a total bugbear of mine and one of the very confusing and difficult parts of losing weight. Trying to figure out what's real and what's advertising whilst desparetly wanting it all to work instantly. And 50 pounds that's fantastic! Well done

  • I really hope this is helpful, and thanks!

  • Alamo, I have always enjoyed your posts, do continue. I need to lose 30lbs so need tips that work. By the way I can only do 3.35 km in 30mins after graduating with c25k, very disheartening so any tips on improvement welcome.

  • Alaiyo not Alamo, sorry

  • Don't be disheartened by your pace of 3.35 in 30 minutes. It is right on target with my own pace. We are at the slow end of the spectrum, but there are lots of possible reasons for that which have nothing to do with our effort. (Joint flexibility, femur length, conditions of our regular route, and a host of other possibles.) With time, you speed will improve, and unless you are really doing this in order to be faster than someone else, going at your natural pace has no real downside - you still get the health benefits, and you still get to call yourself a runner. :)

  • Great blog, thanks Alaiyo.

    As someone who has dieted since age 14 when my Mum told me I was fat, I have always kept an open mind on new theories. However, I have never , ever believed in any fad diet or wonder food.

    I'm an old fashioned kinda gal, i suppose....for example, if you sit on the couch and eat vast amounts of chocolate and drink vast amounts of wine, chances are you're going to be overweight.

    If you get up and exercise, regularly, and are careful what you eat, chances are you're going to be healthier.

    If you follow a strict calorie controlled diet and exercise hard ( outside your comfort zone ) chances are you're going to lose weight.

    I know it's a lot more complicated than that...I'm a trained nurse and midwife, but no nutritional expert.

    But as one medical consultant once said to me "there were no fat people in Belsen and that's because they didn't have anything to eat"....I don't mean any offence by that, but surely its calories in versus calories out, to the non-scientific amongst us ?

    Thanks again for the blog, keep them comimg, always fascinated to learn new stuff...... :)

  • At the very base of it, expending more calories than you take in is "scientifically proven" (lol) to be effective for weight loss. It may not be the only way - there is a lot of debate about other options - but it is a consistently successful start for losing weight, whether fat or lean mass.

  • Great post and a good introduction to science/evidence-based medicine and well done on losing 50lbs!

    One of the good things about this community is that so far I have seen little evidence of "woo", especially around diet. Is it perhaps that this is the natural resting place of those that finally realise that if calories eaten >> calories expended then you get fat whereas if calories eaten <= calories expended then you will lose weight, rather than eating only red protein when the moon is in Aquarius ;-)

  • Wow, I love that. Red meat and astrology... awesome. Probably only works for Pisces though.

  • We virgo`s don`t believe in astrology. :)

  • As usual, a great post. Look forward to the next one. Xxx

  • Very interesting. When I started reading your post I never realised that I was a prime example of Newtonian physics - a largish mass at slow speed..

    You learn something every day!! ;0)

  • ROFL! You and me both, sir. You and me both.

  • Ahem, sorry. You and me both, ma'am. (I saw "Harris" and didn't see your picture. I apologize.)

  • Ah, what a great post, and interesting made simple, once you switch your head on.

    I look forward to the next.

    I think we all pretty much think we know how to be healthy, given current medical knowledge and the info blasted at us on a daily basis, it is the practice of it that is so hard. I am an inherently lazy person and given the choice between lying on the sofa watching the box, or getting on the kit and getting out the door, it's only my sheer stubborness and awareness of the work I've put in so far, that gets me into the lycra. No surrender (to the fat and the lack of fitness) huh?


  • Stubborness and developing good habits is what it is really all about. Good for you for all the work you are putting in, day after day.

  • Great post! I really look forward to the next one. Thank you for taking the time to do that.

  • Crikey, I didn't realise just how thick I was!!! I can't hold that much information in my tiny brain ;) Thanks though, always interested to read different ideas/view points :) It drives me mad reading all the conflicting reports on the best ways to lose weight, I still need to find the answer!! :)

  • Don't feel bad. It is a lot of information - years worth of education, really - crammed into a few paragraphs. It can definitely be confusing out there, which is why I hope to help clear a little bit of it up. :)

  • Great blog, hurry up with the next one please.

    As far as nutrician is concerned if you know of any "Go faster foods" would you please let me know?

  • Ooh, goji berries, gurana, green tea, cacao, mars bars, ;) (ducks from the impending punch from Alaiyo - *jokes*) I used to work in health food stores [whilst studying a proper science degree :) ] oh my do I have some stories - Homeopathic antimalarials anyone?

    I am sure a nutritionist may recommend wholegrain slow release carbs, oats, and nuts and seeds for quick release. (I'd say a Mars bar, but I am slightly 'snuggly'.)

  • There are a lot of good things in health food stores, and some which can best be described as "hopeful". Homeopathic antimalarials! Awesome. I will mix it with my Gin and Tonic, to chase down the chloroquine, and chances are good I will avoid malaria. :) That is a hilarious story I bet!

  • Very interesting and pertinent, need chapter 2 now

  • Thank you - a very elegant explanation of why people should be wary of the scientific claims about one diet versus another and the benefits of exercise.

    I have to say I don't care anymore about whether or not there are health benefits to be gained from running. I just enjoy it!!

    Roll on part two.

  • Alaiyo, I really appreciate that you take the time to drop some knowledge on us in this community. I look forward to seeing your next post.

  • My pleasure! As I go, I find there is so much to share! I posted chapter 2:

  • Good read. I've bookmarked you, looking forward to more. Still see a surprising amount of bad science / politicians trying to prove a point with correlation/causation claims. Funny cartoon :

  • xkcd is probably my favorite web comic, although I am sporadic about reading it. I literally laughed out loud at that one! Thank you. :)

  • interesting

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