1. DeceptionConsider Lies, damned lies and statistics, part n+1. Riera-Crichton et al.
Relative fat intake in %E decreased and obesity increased.
The conclusion:- "Carbohydrates are fattening and fat is slimming." Yeah, right!
Absolute fat intake in grams/kcals increased after healthy eating guidelines (which weren't low-fat guidelines) came out in 1980, according to More Thoughts on Macronutrient Trends.
Gary Taubes & Nina Teicholz use this deliberate misrepresentation of data to create the false narrative that low-fat healthy eating guidelines caused the obesity epidemic in the US. It's a pack of lies.
2. The terms "Low Fat" and "High Fat" are meaninglessTake 55g of fat (500kcals), 125g of protein (500kcals) and 375g of carbohydrate (1,500kcals). It adds up to 2,500kcals, with a percentage C/F/P split of 60/20/20. It's a High Carb, Low Fat diet.
Now remove 125g of carbohydrate to leave 250g of carbohydrate (1000kcals). It now adds up to 2,000kcals, with a percentage C/F/P split of 50/25/25. It's still a High Carb, Low Fat diet.
Now remove another 125g of carbohydrate to leave 125g of carbohydrate (500kcals). It now adds up to 1,500kcals, with a percentage C/F/P split of 33/33/33. It's now a Medium Carb, Medium Fat Zone diet.
Now remove another 62.5g of carbohydrate to leave 62.5g of carbohydrate (250kcals). It now adds up to 1,250kcals, with a percentage C/F/P split of 20/40/40. It's now a Low Carb, Highish Fat diet.
Now remove another 62.5g of carbohydrate to leave 0g of carbohydrate (0kcals). It now adds up to 1,000kcals, with a percentage C/F/P split of 0/50/50. It's now a Very Low Carb, High Fat diet.
So, 55g/day of fat can be Low Fat, Medium Fat, Highish Fat or High Fat. Which leads to...
3. ConfusionWhen someone sees the term LCHF (Low Carb, High Fat), they think it means "Eat less carbohydrate and eat more fat". As changes in bodily stores are determined by Energy Balance, eating more fat leads to a slower rate of weight-loss (or even weight-gain), not a faster rate of weight-loss.
By all means cut the consumption of "bad" carbs, like burgers in buns, chips/fries, crisps/chips, pizza, cake, biscuits/cookies, chocolate and sugar sweetened beverages.
However, if you believe that "good" carbs like vegetable produce, legumes, whole grains and whole fruits make you fat and sick, you need to have your head examined, unless you're in the tiny percentage of the population who have genetic carbohydrate intolerance.
See also Insulin Resistance: Solutions to problems.