Science Catch-up. Is ‘Portion Control’ the Right Message? Probably Not…

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by Alejandra "Alex" Ruani — Get free science updates here.

Welcome to our Thursday’s Science Catch-up: curated links by The Health Sciences Academy. Get our email updates every other Thursday here (it’s free).

Let’s catch you up with studies and news that recently made the headlines!

Click on your favourite topics to read our summary:

1. Is ‘portion control’ the right message? Probably not…

2. Stop counting calories and start promoting nutritional value, urge researchers

3. Adaptation to high-fat diet had profound effect on genes

4. Omega-3 could help support ‘friendly bacteria’ in the gut

5. The amazing significance of what a mother-to-be eats

6. Banning trans fats in England could prevent 7,000 heart deaths over next 5 years

7. Is this why Americans are getting fatter?

8. India orders sugar producers to ramp up exports to curb surplus

9. Reducing sugary drink intake is linked to raised HDL cholesterol levels

10. Balancing the evidence: Fresh study suggests negative impact of saturated fats

11. High genetic risk individuals benefit less from resistance exercise intervention

12. Volunteers who stayed in bed for a week and ate 6,000 calories of pizza and burgers every day in the name of science developed medical issues in just two days


Is ‘portion control’ the right message? Probably not…

The BBC reported that “Reducing the portion sizes… would help reverse the obesity epidemic”.

This is another case where the media didn’t report study findings accurately.

The BBC journalist based this statement on a systematic review (“a study of studies”) that analysed 72 studies on portion/packaging/tableware size (note the journalist wrote “61” studies).

When I read the systematic review, I noticed that it didn’t examine weight gain, satiety or food intake in subsequent meals, and the participants in most studies were not even trying to lose weight. So, where’s the “reversal of obesity epidemic” claimed by the media?

What the systematic review did analyse was portion size in connection with the risk of overeating, estimating that if smaller portion sizes are used consistently across meals, the average calorie intake in adults could reduce by 215 to 279 calories per day.

But is “eating less” the actual message of this systematic review?

Not really…

The researchers’ eat less message is pointed towards “high-energy-dense” foods like chocolate bars, dessert, cookies and fast food, but not towards “low-energy-dense” foods like vegetables.

High-energy-dense foods are foods that have more calories per gram – vs low-energy-dense foods, which have less calories per gram.

NHS Choices also wrote about this systematic review and stated that “Decreasing portion sizes could cut obesity levels”, which is a somewhat incomplete message too. After the words “portion sizes” we’d need to add “of high-energy-dense foods” to accurately reflect the findings.

This is an important distinction, because urging people to simply eat less of “any” food may not be the best approach.

The “portion size effect” shown in here can also be used the other way around, to your benefit, e.g. a bigger serving of vegetables to eat more of them. In fact, that’s part of the conclusion which the media and the NHS omitted.

Here’s what the researchers actually wrote in the systematic review (sadly skipped by the news outlets):

“… [these findings ] are consistent with the proposal that a ‘portion size effect’ is still present when people are exposed to larger sizes of healthier and less energy-dense foods, suggesting that interventions that successfully increase people’s exposure to larger portion sizes of healthier, low energy-dense foods such as vegetables may still be an effective strategy for increasing consumption of these foods.”

This paragraph is a gem!

Why? Because portion control doesn’t work for everyone, particularly those who enjoy eating until complete satiation or have a “plate cleaning tendency” (as the researchers call it), which are completely normal traits and totally manageable if you add more plant-based foods and healthier, less energy-dense meals into your diet.

The bottom line is that eating less of “any” food is not the best (or only) way to successfully decrease obesity levels in the long term.

As Dr Rolls puts it in one of my favourite pieces of research:

“A more effective strategy may be to encourage people to increase the proportion of foods low in energy density in their diets while limiting portions of high-energy-dense foods. If people lower the energy density of their diet, they can eat satisfying portions while managing their body weight.”

Here are the links to the (full text) scientific papers:

Portion, package or tableware size for changing selection and consumption of food, alcohol and tobacco. Hollands et al., 2015. Cochrane Database of Systematic Reviews.

What is the role of portion control in weight management? Rolls, 2014. International Journal of Obesity.


Stop counting calories and start promoting nutritional value, urge researchers

News link

As I always say: before we jump to conclusions, let’s look at the context in which things are written. In this case, the context is health policy in relation to heart disease and mortality.

This news headline is connected to a commentary written by researchers who believe that focusing only on calories (and not nutritional value) has been exploited by the food industry, which has added sugar to over 80% of all processed foods. They urge that health messages and political solutions should focus on promoting simple changes that improve the nutritional value of consumers’ diets. These solutions include taxing sugary drinks, subsidies to make plant-based foods more affordable, and more control on the marketing of junk food.

The researchers said that “the evidence indeed supports the mantra that food can be the most powerful form of medicine or the slowest form of poison.”

I’m not a fan of using the word “poison” in the context of nutrition (given the psychological “nocebo effect” that words can have on us), but in the big scheme of things I think they are just trying to get their point across.


Adaptation to high-fat diet had profound effect on genes

News link

Interesting new data suggesting that Inuit populations (i.e. Eskimos) developed genetic mutations about 20,000 years ago to counterbalance the bad health effects of their high-fat diet. This is another great example of nutrigenomics, meaning that not all of us may be able to tolerate a high-fat regime.

The scientists discovered that most Europeans and Chinese in their study didn’t carry the same protective genes against high-fat consumption.

All of this reminds us that we shouldn’t get fixated on a single nutritional dogma. Each individual responds differently to different diets. Because of your unique genetic makeup, you metabolise nutrients differently, and what works for you may not work for someone else. For more on nutrigenomics, we have a few Science Reports for our advanced readers: 1) Coffee and Your Genes; 2) Folate and Your Genes; 3) From Food to DNA.


Omega-3 could help support ‘friendly bacteria’ in the gut

News link

Research on gut microbiota keeps getting more interesting. In this preliminary research, scientists discovered that a type of Omega 3, EPA (eicosapentaenoic acid), which is found in oily fish, may support the growth and survival of probiotic bacterial strains that help reduce inflammatory responses.


The amazing significance of what a mother-to-be eats

News link

Respected BBC journalist, Dr Michael Mosely, talks about the impact that your mom’s diet (at the time of your conception) has on the rest of your life. Dads-to-be, don’t think you’re off the grid: epigenetic imprinting on reproductive cells before conception also counts!


Banning trans fats in England could prevent 7,000 heart deaths over next 5 years

News link

This is an interesting projection. Just be mindful that any study that uses a mathematical model relies on the researchers making correct assumptions when they feed in the data, and in some cases this data may be limited. For example, in this projection we don’t know what proportion of trans fats are consumed in restaurants or fast food outlets, so we’re talking about “guesstimates”.

In any case, we know trans fats are a danger to health – so we anticipate the UK and other countries will follow the US lead in banning them.


Is this why Americans are getting fatter?

News link

I didn’t expect this one. It seems that, on average, each American ate around 5.6 pounds (2.54kg) of butter last year, up from 4.5 pounds (2kg) in 2000. A lot! Of course, we can’t blame a single ingredient, it’s often the compounded effect of your overall diet and lifestyle which affects fat gain.


India orders sugar producers to ramp up exports to curb surplus

News link

Looks like India is producing a surplus of sugar, so local producers are pushed to ramp up their exports to at least 4 million tonnes in the forthcoming crushing season, to cut stockpiles in the country.


Reducing sugary drink intake is linked to raised HDL cholesterol levels

Study link

HDL cholesterol is known as the “good” cholesterol. High-density lipoproteins (HDL) act as “bad” cholesterol scavengers, picking up excess LDL cholesterol in your blood and taking it back to your liver where it’s broken down. The higher your HDL level, the less “bad” cholesterol you’ll have in your blood. In this study, it seems that lowering the consumption of sugar-sweetened drinks by at least one serving per week could help to improve these markers of cholesterol.


Balancing the evidence: Fresh study suggests negative impact of saturated fats

News link

Saturated fat research has primarily focused on heart disease risk, with several recent studies exonerating it (see here). However, this new study from scientists at Imperial College London put saturated fat under the spotlight (again!). It seems that high concentrations of saturated fats (in the form of triglyceride-rich lipoproteins that contain saturated fatty acids) could lead to an increased risk of inflammation and tissue damage. Bear in mind that it’s a mice (and not a human) study, but it could open the doors to new investigations. So yes, the saga continues!


High genetic risk individuals benefit less from resistance exercise intervention

Study link

This 1-year study involving 148 women showed that those with a high genetic predisposition to obesity didn’t benefit as much from resistance training (in terms of fat loss), compared to those with a low genetic predisposition.

Although the fat loss from resistance training varies depending on a person’s genetic risk for obesity, don’t hand your trainers in just yet. There are other genes that also influence your athletic status and we examine them in our latest Science Report: How Genetic Is Your Exercise Level – Or Lack Of? – where you can take an exercise self-assessment at the beginning to measure your own level.


Volunteers who stayed in bed for a week and ate 6,000 calories of pizza and burgers every day in the name of science developed medical issues in just two days

News link

This Daily Mail headline is sensationalistic but somewhat accurate. In this trial, 6 healthy men were confined in a tiny room and overfed 6,000 calories a day for a week. On day 2, they showed signs of increased insulin resistance and oxidative stress. Not good. By day 7, they gained an average 3.5 kg, primarily body fat.

I think it makes an entertaining story, but just remember that 6 participants cannot show us “conclusive” evidence. Say that we carry out the same experiment with 6 Olympic athletes, the results would probably be completely different. Also, the researchers didn’t use a “control” group for comparison, which kind of discredits the results.



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What has inspired you this week? What are your thoughts on some of these topics? Leave a comment and let us know!

Alex Ruani leads the research division at The Health Sciences Academy, where she and her team make sense of complex scientific literature and translate it into easy-to-understand practical concepts for students. She is a Harvard-trained scientific researcher who specialises in cravings and appetite neurobiology, nutrition biochemistry, and nutrigenomics. Besides investigating and teaching the latest advances in health and nutrition science, Alex makes it easier to be smarter with her free Science Catch-ups every other Thursday.
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  • Cathy Johnson Campbell

    Reply Reply September 25, 2015

    Hi there,
    I’m a raving fan of your website and excellent research.
    However, one headline/summary this week thinks you might have missed the point. “Is this why Americans are getting fatter?” You say… “It seems that, on average, each American ate around 5.6 pounds (2.54kg) of butter last year, up from 4.5 pounds (2kg) in 2000. A lot!”.
    Actually, 5.6 pounds of butter is still less than 1/2 what the American Heart Assoc (AHA) recommends acceptable levels of saturated fat consumption. I calculated this by: 2000 calorie/day allows 120 calories in saturated fat as per AHA. 1 T butter = 102 calories so an average person can happily enjoy 1 T butter per day, yes? 1 lb butter = 32 T. Therefore 5.6 lb butter = 179.2 T. That’s only 179 days worth of butter, or about 1/2 T butter per day for a year. Meaning, there’s still room for another few pounds of butter per year.


    This is not to say I believe AHA are the definite source on a healthy diet. But there is research supporting the benefits of butter, and indicating it’s neither the cause of obesity nor heart disease.

    Hopefully, people will make their consumption of butter from organic free range grass fed cows.

    Keep up the great work!

    • Thanks so much for your lovely feedback, love to hear that :-)

      It’s hard to say since people can also consume saturated fat from other sources like meat, cheese, eggs, coconut oil, bacon, milk, yogurt, cream, lard, dark chocolate, palm oil, bread, bakery, pastries, ice cream, processed foods, and so on.

      This news headline is in the context of obesity/fat gain rather than heart health, and to date there’s no evidence indicating that butter/saturated fat doesn’t cause fat gain… other than in the generic context of energy restriction or in strict ketogenic/low-carb diet studies, but most Americans don’t follow a ketogenic diet – stats show a high-sugar and high-carb consumption, so we need to look at the compounded effect of a person’s overall diet.

      We also need to consider that the results of most studies are based on averages. New research shows that “on average” saturated fat does not raise the risk of heart disease.

      However, within those averages, there’s room for individual variability. Some individuals may see no effect, while others may experience an increased risk.

      There are definitely some individuals who may want to minimise saturated fat in their diet. This includes those with a genetic disorder called Familial Hypercholesterolemia and those who have a specific variant at the APOE gene (epsilon3 and epsilon4 alleles).

      Nutrigenomics is constantly discovering more ways in which certain foods affect our individual risk for disease, that’s why general findings may not apply to everyone so I always like to keep an open mind.

      All of this reminds us that nutrition science is not black and white and that’s an evolving field, which I personally find quite exciting :-)

      • Cathy Johnson Campbell

        Reply Reply October 10, 2015

        Good points Alex.
        And a great reminder… The unmeasured compound affects, and variability within averages does make certain nutrition science is not black and white.
        Thanks for your response.

  • Ron watson

    Reply Reply September 26, 2015

    If they are measuring the consumption by the increase production of butter, it’s possible it’s the fear of trans fat in margarine. I know I switched to butter about 7 years ago because of it. I mentioned it to my family doctor and he said to stay on the butter. Lesser of the two evils.
    So there may be a corresponding decrease of margarine use with all the media talk of trans fat.

    By the way Alex, great work on the materials and information you share. I really enjoy it.


    • Ron – good points re margarine/trans fats :-) I’m delighted to hear you enjoy the materials, it’s a pleasure to prepare them for you!

  • Emily

    Reply Reply October 10, 2015

    Dave Asprey has become famous for rallying the nutritional benefits of butter, namely butyrate and CLA. He and many leading experts in the field of nutrition promote copious amount of grass-fed butter for the Average American diet. Do you think these studies would be different if there were a distinction made between convention butter and butter from grass-fed cows?

    • Hi Emily – We know that milk and its derivatives from cows grazing pastures are more beneficial than those being grain fed, eg they have more betacarotene, vitamins, CLA, omega 3, etc. But you can also get your butyrate, omega 3, CLA, betacarotene and vitamins from other sources that are much richer in those nutrients (plus others) than butter/cheese. For example, butyrate is created by your gut bacteria when exposed to dietary fibre, so if you eat sufficient fibre from vegs you’re covered, plus you get tons of phytochemicals along the way. CLA is a type of omega 6 (i.e. un-saturated) that you can get from sesame seeds, wheat germ, walnuts, vegetable oils, etc. So it comes down to a personal choice (except for those who are lactose intolerant and have no choice). Science works in a very granular way and tests only one thing at a time, but we need to think of the compounded effect of our overall diet as opposed to a single food in isolation if you know what I mean :-)

      • Rob

        Reply Reply October 23, 2015

        thanks for the great info! i enjoy reading your comments too, very balanced and fresh; not the typical ‘bro science’ that contaminates the internet!

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