[mi100hael]

> He says something similar may happen in human brains when people eat a diet high in fat and sugar. Davidson says there's a vicious cycle of bad diets and brain changes. He points to a 2015 study in the Journal of Pediatrics that found obese children performed more poorly on memory tasks that test the hippocampus compared with kids who weren't overweight.

These assertions raise doubts in my mind regarding the study as a whole. Fat and sugar (a carbohydrate) account for two of the three most common macronutrients, the third being protein. Eating a diet that's low in both fat and carbs would imply a mostly-protein diet which can lead to illness[0].

The further implication that a particular macronutrient ratio could cause obesity is particularly concerning. Weight gain/loss is determined strictly by whether someone consumes more or fewer calories than their body burns in a day. The ratio of macronutrients may effect other health indicators like lean body mass, but a diet of 100% sugar and fat will still lead to weight loss if the total caloric intake is lower than what the body requires thereby requiring the body to burn muscle/fat for energy[1].

While the researchers have found a correlation between memory function and obesity, they appear to be making spurious claims that the foods the obese people eat are a contributing factor. There's no indication they made any attempt to control for the fact that healthy people also regularly enjoy ice cream and bacon, just at a lesser rate than those who are chronic over-eaters and therefore obese.

[0] https://en.wikipedia.org/wiki/Protein_poisoning [1] http://articles.latimes.com/2010/dec/06/health/la-he-fitness...

[bitwize]

This is the "a calorie is a calorie is a calorie" argument, and it's not true. Sugar upsets the metabolic process in disconcerting ways, leading to fat accumulation and insulin resistance; sugar is also more addictive than cocaine[0]. Meaning that when you consume calories from sugar, you crave more sugar calories. The foods you eat do make a difference in how fat you get, because they alter your metabolism and behavior -- but Western foods are so loaded with added sugar that sugar becomes difficult to control for.

[0] https://www.ncbi.nlm.nih.gov/pubmed/23719144

[another_account]

Yes, macro break down, thyroid issues, metabolism, illness, meal timing, GI, insulin spikes, hormone levels etc do make a difference. To grab at a generous figure lets say they make up 25% of the puzzle. With calories in VS calories out been 75%. And i think that 25% is very, very generous.

Stating calories in VS calories out is not true because of X, Y or Z is like building a house by starting with the doorbell. Before you lay the foundations. Fundamentals before details.

[mi100hael]

The "calorie is a calorie" argument is true in that

    weight gain/loss == surplus/deficit intake

Your point about sugar fucking with insulin balance and its addictive properties are good points, but not directly related to the study at hand. Western prepared foods are loaded with added sugar, but it's completely possible for obese people to eat a complete diet of home-cooked meals in surplus using only fresh, raw ingredients without a gram of added sugar. It's also completely possible for skinny people to eat shit food and not get fat. The researchers should have controlled for body fat % and diet, which would not have been challenging. Instead it seems they've chosen to completely conflate the two key factors.

[dualogy]

> Fat and sugar (a carbohydrate) account for two of the three most common macronutrients, the third being protein. Eating a diet that's low in both fat and carbs would imply a mostly-protein diet which can lead to illness

Spot-on observation. Furthermore, while proteins can be metabolized for energy, that's not advisable as a major energy source, proteins should be spared for day-to-day repairs (most-all multicellular structures ---incl tissues/bones/organs/tendons, the brain, not just simply "the muscles"--- are constantly tearing-down and rebuilding and we also synthesize much other crucial stuff partially from amino acids, red/white blood cells, enzymes, the list goes on, even glucose if&as necessary) and burning them instead not just removes them as building materials but also creates various additional stresses on the body, produces extra detrimental waste products to be run through the kidneys and get excreted, etc.

All mammals excel at beta-oxidation of both carbohydrates and fatty acids for energy, I know of no animal thriving off the meagre amount of energy their bodies may safely obtain from proteins. Many humans don't seem do particularly well (in the long run) combining fats & carbs in ~equally high amounts and find better results emphasizing one and sharply reducing the other. (Personally I'm a fat advocate but no need to get into that discussion ;)

Consider 2000kcals from protein-only (not that your body will allow this) would require 500g of protein, so about ~2kg of super-lean meat or over 100 egg-whites.. and that's not yet counting any protein usage as building-blocks!

[emodendroket]

> The further implication that a particular macronutrient ratio could cause obesity is particularly concerning. Weight gain/loss is determined strictly by whether someone consumes more or fewer calories than their body burns in a day. The ratio of macronutrients may effect other health indicators like lean body mass, but a diet of 100% sugar and fat will still lead to weight loss if the total caloric intake is lower than what the body requires thereby requiring the body to burn muscle/fat for energy[1].

Perhaps, but people in the real world don't usually carefully measure out a portion based on calories before consuming; they eat until they're not hungry anymore. So any food that is calorically dense but doesn't satisfy hunger is likely to contribute to obesity.

The government warns against fats and sugars for similar reasons here https://health.gov/dietaryguidelines/dga2010/dietaryguidelin...

[hx87]

Fats are pretty damn filling, even when caloric density is accounted for, at least for me.

[emodendroket]

Well I think that's a big part of why the focus lately is moving to sugars over fats. But the other point is that they're not very rich in nutrients.

[mi100hael]

Unsaturated fats are essential for brain function & health. Increased consumption has been linked to a reduced risk of dementia and Alzheimers.

[emodendroket]

It's saturated fats and trans fats in particular that everybody is warning you off, not lipids altogether.

[xiaoma]

There's a huge difference between various carbs. In the 90s both Japan and developing countries in east Asia had absolutely massive rice intakes and extremely low rates of obesity, and high longevity.

According to studies I've read, many people got 1/2 to 2/3 of their total calories just from rice. You can't do that with sugar and lead the world in longevity rates.