[brettv2]

> I've never seen anyone who's obese and having a diet that made me go "huh that's odd how can they be obese?"

Your question isn't refuting OPs claim: the people you are observing to be fat are fat because of their carb/sugar intake, not fat.

i.e. if you just fed someone large amounts of protein and fat they would be lean; it is the sugar and carbs that make them fat.

[jlhf]

No they wouldn’t stay lean. If you fed someone more calories than their body uses to maintain its current weight, they would get fat eventually. Regardless of whether they eat carbs, fat or protein.

[kuschkufan]

Let's say you're being fed just the amount of calories your body needs to maintain. What influence on body fat has the distribution of carbs, protein and fat from food then?

[jlhf]

My point was that regardless of what you eat, if you eat more than your body expends, some of the excess will be used to produce fat and you will gain weight. If you lead a sedentary lifestyle and eat 3000 calories of nothing but lean meat per day, you will gain weight.

You are right that different foods (macronutrients, more specifically) have different thermic effects and therefore require different amounts of energy to metabolise. Protein takes more energy to process than fat. This does not change my overall point.

[lobocinza]

Not much for getting lean but it's easier to overeat carbs and fats are calorie dense. That said you need to eat a mix of the three to be healthy because they all have important body functions.

[burjui]

Lack of carbs supresses appetite, JFYI.

[jlhf]

I never claimed otherwise and it does not negate my point.

[jbd0]

You're so wrong. With only protein and fat, they would not be able to gain much weight. I've tried to gain weight on low carb/high fat, and it doesn't work. I was uncomfortably full after every meal. My tracking showed a significant calorie surplus, but my body wasn't absorbing it. Adding in more carbs made a huge difference. Hormones tell your body when to store fat.

[Attummm]

Did you know that bodybuilders in the 1950's(before anabolic steroids) used the egg and steak diet before contests as cutting diet to get lean? They would eat, as the name suggests, large quantities of steak and eggs with butter and have a carb refeeding day every 4 days. They would get really lean on a very high-calorie diet, think 4000 to 6000 calories.

The inventor of diet famously lost a contest for being too lean.

[callmeal]

> if you just fed someone large amounts of protein and fat they would be lean;

A large amount of protein would make them fat - experiments have shown that about 8% of ingested protein gets converted to glucose in the liver:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3636610/

    The authors calculated that ∼18 g (79%) of the 23 g of ingested protein could be accounted for by deamination; thus those carbon skeletons were available for gluconeogenesis and release of new glucose into the circulation. The remainder, presumably, was used for new protein synthesis.

    The total amount of glucose entering the circulation from all sources was calculated to be 50 g over the 8-h period. However, only 4 g (8%) could be attributed to the ingested protein.

[amanaplanacanal]

I think you misread that experiment. It appears that some quantity of protein was converted to glucose, but that it wasn’t dependent in the quantity of protein consumed.

[cies]

Humans are bad at lipogenesis: we can only convert tiny fraction of the carbs into fat. Thus: the fat your eat is largely the fat you wear.

You cannot explain it otherwise (without showing a undiscoverd way humans can convert carbs into fat).

> i.e. if you just fed someone large amounts of protein and fat they would be lean; it is the sugar and carbs that make them fat.

This is dangerous. It may work on the short term, but it is very dangerous on the long run.

[mpreda]

> Humans are bad at lipogenesis: we can only convert tiny fraction of the carbs into fat.

Because historically food is scarce or difficult to obtain, in general organisms develop mechanisms to make good use of it: when excess food ("energy") is available, it is stored rather than wasted.

This is also true in particular for mammals, and for humans. It's quite obvious that humans are very effective at storing excess energy.

It is said that sumo fighters maintain their body mass (muscle + lots of fat) by eating rice (i.e. carbohydrates) and protein.

Lipogenesis (fat generation from carbohydrates) takes place mostly in the liver. "Excess acetyl CoA generated from excess glucose or carbohydrate ingestion can be used for fatty acid synthesis or lipogenesis."

https://courses.lumenlearning.com/suny-ap2/chapter/lipid-met...

The conclusion being: "Humans are great at lipogenesis. That's how we store excess energy."

[cies]

Nope. If humans eat both carbs and fat (most of us do), the excess calories of fat goes mainly into the storage (or plaques to your arteries), while the carbs are used in the sort term (converted into glucose).

> Lipogenesis is mostly derived from carbohydrates and is a relatively minor contributor to whole-body lipid stores, contributing 1–3% of the total fat balance in humans consuming a typical diet.

From:

https://www.sciencedirect.com/topics/agricultural-and-biolog...

Believe what you will. "It is said" wrt sumo fighters does not sound very scientific.

[Attummm]

The human body doesn't need to store excess calories. It could store the excess calories or it can excrete energy through urine(glucose, ketones) Or it can ramp up metabolism, there are many scenarios. Not all lead to adipose tissue growth. Why not muscle growth, which is somehow always overlooked in these discussions.

Funny enough adipose tissue and muscle growth are both through hormones. If testorone and hgh are high then muscles growth will prioritised over adipose tissue.

People with type 1 diabetes have figured out how to stay thin after eating copious amounts[0]. They won't inject themselves with insulin. Unhealthy, sure, but they won't store calories, as adipose tissue (fat cells) remain inactive, even though blood glucose is dangerously high.

Just looking at calories is simplification, and is just for general guidance.

[0]https://my.clevelandclinic.org/health/diseases/22658-diabuli...

[Attummm]

Why would a mammal's body evolved to use fat cells to store and utilise lipids for energy?

Plants have carbs in starch. Mammals evolved away from starch to store and use triglycerides.

During fasting, the human body is able to survive for months without food.

Thus months of lipid metabolism

[cies]

> Why would a mammal's body evolved to use fat cells to store and utilise lipids for energy?

Hibernation?

For short term glucose storage is preferred by mammals bodies that i know of.

[thelittleone]

High fat and protein is keto right? What's so dangerous?

[cies]

Ketosis is probably our rudimentary "wintersleep mode". Rudimentary as we are basically tropical animals (look at our lack of fur).

We should not eat for ketosis. But we can eat (restricted to fat and protein) and still stay in ketosis, which is marketed as the keto diet and is not well tested in long term studies. You are a guinea pig when you do this long term.

[imtringued]

>You are a guinea pig when you do this long term.

As opposed to being reliably obese? What's your baseline? I recently checked the average weight of men and women and I am honestly shocked.

[cies]

Short term you can lose weight with ketosis. Long term you are taking unknown risks.

The risks of obesity are well known. Also, you do not get obese by lack of a keto diet. One usually gets there with a rubbish diet.

[thelittleone]

For me I went keto because I had a problem with sugar addiction going back since childhood. I managed to maintain a healthy weight through exercise etc but as I aged I felt that my bodies ability to handle sugar was decreasing, and it had significant impact on my energy levels, physical appearance and digestion.

Keto not only simplified my diet but massively improved my digestion, and helped me form more awareness of risks of sugar.

Regarding no long term studies.. its hard to believe much these days I rely on body feedback. Years ago the American diet was supposed to be healthy, look how that science turned out.