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:
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?
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
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
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
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
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
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?
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
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
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
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
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
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!