Surwit and sucrose or when is a high sucrose diet a high fat diet?

Last one liner post and I'll try and get to older comments as soon as I can:

The name Surwit is familiar. I have this niggling feeling that I've come across it before. There's no inclusion of the name on the blog except as the name for an obesogenic mouse diet based on sucrose. I have this feeling it was someone pointing out that a high sucrose diet was perfectly acceptable if you kept PUFA low. Can't find it. Don Matesz brought the paper to light recently by discussing it over at Primal Wisdom. It's a core paper on why you should be cautious about simply accepting conclusions from papers without thinking them through.

I just wanted to pour a little arithmetic on Surwit's paper from 1997.

The 1100kcal diet was 70% carbohydrate, ie 770kcal/d or approx 180g/d.

Protein was held at about 50g/d and fat was held at around 10g/d

Let's look at calories-in and calories-out.

With a weight loss of 7kg in 6 weeks these people were augmenting their diet calories-in by adding an additional 167g/ day of fat from their own adipose tissue (assuming weight loss is fat loss, not quite true). This gives an average "calories-in" of 1100kcal from diet plus about 1670kcal/d from adipose tissue, ie a total of 2670kcal per day going in to metabolism.

Calories-in of 10g fat from the diet plus 167g/d of fat from adipose tissue, with a total of 2670kcal per day used, gives us a metabolic input comprised of 66% from FAT.

120g/d of sucrose is about 540kcal/d which actually makes this only about 20% of the "calories-in" to metabolism, with fructose at about 10% of calories.

The study subjects are obese which, trans fats apart, suggests that they are probably eating a great deal more sucrose per day during their habitual diet than 120g (and failing to deal with it effectively). So, in comparison to their pre study diet, this is probably a LOW SUCROSE diet. A Big Gulp is about 800kcal per serving of HFCS... At 180g/d the study diet is also a LOW CARBOHYDRATE diet compared to their pre study intake. You do not "accidentally" maintain a bodyweight up near 200% of ideal unless you have a carbohydrate intake waaaaay in excess of 180g/d. Just flick through the introduction to Grey and Kipnis yet again. Obese people eat more calories and especially more carbohydrate calories than normal weight people.

Now, let's stop weight loss occurring and think about health on a 34% sucrose diet. Let's up the calories-in from 1100kcal/d to 2670kcal/d to (possibly) maintain a stable weight (it won't happen, weight will rise secondary to increase insulin levels associated with a fall in spontaneous activity) but this time let's source all of those calories from the diet. With 34% of calories as sucrose that will be just under 300g/d of sucrose. That gives an annual intake of just over 100kg, about a tonne in 10 years. HDL is already down from 1.35mmol/l to 1.06mmol/l (if you think it matters) and if you think trigs will stay at just over 1.00mmol/l on a third of a kilo of sucrose a day you are incorrect. Will the drop in blood pressure be maintained? Hahahahahahaha. Do you want to try this?

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BLACK BOX HEALTH WARNING: The next line is sarcasm.
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I'm sure it would be fine, just ask Surwit.

You can't lose weight for ever. Weight loss is fat metabolism. When weight stabilises how do you maintain the benefits of fat metabolism? Hint: Don't replace it with sucrose.

Peter