Evolving evidence about diet and health, 2018, Mente et al, Lancet

https://www.thelancet.com/journals/lanpub/article/PIIS2468-2667(18)30160-9/fulltext

• Andrew Mente
• Salim Yusuf

Volume 3, ISSUE 9, Pe408-e409, September 01, 2018

 

Seems to me like it’s a ‘stop the insanity’ kind of article. Finally.

 

Interesting observation I thought, when you ponder how BPS group thinking seems pervade their ME research, supposedly reinforcing the validity of study A's findings because it tallies with the previous findings of studies B, C, D, etc.

 

All dietary recommendations should be taken with a pinch of salt. Or a sprinkling.

 

Whilst this is ok and interesting as with the fat study they also make some pretty broad correlations.

They do go on to describe a sensible balanced approach. The elephant in the room though, is the lack of objective studies looking at the broader socioeconomic factors that impact obesity in the general population (eating out, less physical jobs in employment, increasing portion sizes etc etc).

The key problem for researchers in this area is the eating out element. It seems highly dubious to draw the conclusion that medical advice on fats vs carbohydrates is the reason for the epidemic in obesity over the last 20 years. It’s more complicated than that.

So whilst it’s good not to demonise or restrict certain food groups (fats or carbohydrates), it is unlikely to change the fact that people eat too much for their calories out. So that is the main issue I think notnso much the balance of foods we eat. There are some interesting studies on satiety but again focusing on this is avoiding that annoying more uncomfortable elephant.

Eating saturated fat does still increase blood serum cholesterol if you eat too much of it, so restricting calorie consumption to what you need is still the best policy, and whatever diet you are following, blood serum cholesterol results being too high is a strong indicator that you should change your diet in some way.

What the authors fail to recognise is that public policy is not just based on a perfect scientific model, it has to consider other factors. We are now more aware of cholesterol than we were 40 years ago for example and I think that is a good thing?

The main problem for researchers in studies on obesity is getting enough power to their data to be representative. This is particularly the case with eating out of home data. Many of us snack too much in between meals and a lot more of our food is consumed out of the home than it was 20 years ago.

Objective data collection in this area (from till sales and nutritional breakdown of meals) is poor compared to retail grocery sales. Studies show that we underestimate calories for our out of the home food more than we do in the home. There are also indications that portion sizes have been increasing for all convenience foods over the last 10 years. This creates a big problem in biased reporting for questionnaires etc. In any case, no one wants to report that they are eating too much, so questionnaire results on food diaries etc will always be reporting low.

I suspect that overeating calories out of the home is likely to be a massive contributing factor to obesity in the western world. Public health England recently admitted that they failed to collect this data correctly and so don’t actually know what we consume here with any certainty.

I doubt that anything but tighter regulation on labelling in the out of home market and better till data collection will make this change very soon.

 

The correlation between poor diet and poor health is mediated by the weight variable. Making a causal link between poor diet and poor health, might be obvious. However, there are many instances of people with poor diets who are healthy. A causal relation between high body fat levels and poor health on the other hand, is almost certain to exist. I've read many weight loss studies, comparing various diets. What was universally found: decreases in cholesterol, improved cardiovascular parameters, etc. regardless of the diet employed.

Very often, studies will claim: 'A diet high in X will cause health problem Y.' While failing to mention that a diet high in X also promotes weight gain, and weight gain causes problem Y, so in essence Y was not directly caused by X, but by the weight gain. This faulty logic can very misleading and promote many fad diets.

This is why it is very important that research controls for weight gain when making conclusions. In other words, it needs to be determined how much of the effect was directly due to the diet and how much was due to the weight gain or loss caused by the diet.

Finally, it needs to be emphasized how important it is to mantain a healthy weight. Hundreds of different chemical compounds and diets have been touted as lifespan extending. Despite this, none of them have been able to extend life span in animal studies to a significant degree. There is only one thing that has been consistently proven to extend life span and it is not a diet or a compund. What is it? Caloric restriction. Numerous animal studies have proven this: low calories increase lifespan, excessive calories reduce it. So in conclusion, what matters most is not what you eat, but how much you eat of it.

 

Healthy weights may be a bit of a misnomer. The rise of the TOFI ( thin outside fat inside) whilst some overweight individuals are metabolically healthy suggests a complexity that does not lend itself to broad generalisations.
The type of adipose tissue and its role in signalling seems to be a key issue.

 

What do you think of the "healthy at every size" movement?

https://www.google.com/amp/s/www.huffpost.com/entry/can-you-be-healthy-at-eve_b_7905358/amp

 

In my opinion that idea is totally wrong. There's just too much evidence to the contrary. It might be possible that some people are healthy despite being obese, but those would be the exceptions, not the rule. An analogy would be a person who smokes all their life and lives to be 90, yes it happens, but it's a terrible thing to do for the average person.