From this study (De novo lipogenesis during controlled overfeeding with sucrose or glucose in lean and obese women. Regina M McDevitt, Sarah J Bott, Marilyn Harding, W Andrew Coward, Leslie J Bluck, and Andrew M Prentice. Am J Clin Nutr 2001;74:737–46.):
Thus, an excess amount of carbohydrate stimulates de novo lipogenesis significantly more than does an isoenergetic quantity of fat.
When measured directly, de novo lipogenesis is strongly influenced by the macronutrient composition of the diet, even in the absence of excess energy, and can increase dramatically under certain dietary conditions. De novo lipogenesis increased 5-fold in lean subjects fed a low-fat, high-carbohydrate diet (70% carbohydrate, 10% fat) compared with a typical Western diet containing 45% carbohydrate and 40% fat.
This is a really interesting finding:
One of the aims of the present study was to evaluate the difference in de novo lipogenesis between lean and obese women under both control and overfeeding conditions. We found that de novo lipogenesis was significantly higher in the obese subjects than in the lean ones when subjects were fed to energy balance. However, this difference disappeared during conditions of overfeeding.
So it turns out it isn’t fat that makes you fat, but carbohydrates?
Yet another study (Hepatic de novo lipogenesis in normoinsulinemic and hyperinsulinemic subjects consuming high-fat, low-carbohydrate and low-fat, high-carbohydrate isoenergetic diets. Jean-Marc Schwarz Peter Linfoot Doris Dare Karmen Aghajanian. The American Journal of Clinical Nutrition, Volume 77, Issue 1, 1 January 2003, Pages 43–50):
Design: After 5 d of an isoenergetic high-fat, low-carbohydrate diet, fasting DNL was measured in normoinsulinemic (≤ 85 pmol/L) lean (n = 9) and obese (n= 6) and hyperinsulinemic (≥ 115 pmol/L) obese (n = 8) subjects. Fasting DNL was measured after a low-fat, high-carbohydrate diet in normoinsulinemic lean (n = 5) and hyperinsulinemic obese (n = 5) subjects. Mass isotopomer distribution analysis was used to measure the fraction of newly synthesized fatty acids in VLDL-triacylglycerol.
The results were:
Results: With the high-fat, low-carbohydrate diet, hyperinsulinemic obese subjects had a 3.7–5.3-fold higher fractional DNL (8.5 ± 0.7%) than did normoinsulinemic lean (1.6 ± 0.5%) or obese (2.3 ± 0.3%) subjects. With the low-fat, high-carbohydrate diet, normoinsulinemic lean and hyperinsulinemic obese subjects had similarly high fractional DNL (13 ± 5.1% and 12.8 ± 1.4%, respectively). Compared with baseline, consumption of the high-fat, low-carbohydrate diet did not affect triacylglycerol concentrations. However, after the low-fat, high-carbohydrate diet, triacylglycerols increased significantly and DNL was 5–6-fold higher than in normoinsulinemic subjects consuming a high-fat diet. The increase in triacylglycerol after the low-fat, high-carbohydrate diet was correlated with fractional DNL (P < 0.01), indicating that subjects with high DNL had the greatest increase in triacylglycerols.
Conclusions: These results support the concept that both hyperinsulinemia and a low-fat diet increase DNL, and that DNL contributes to hypertriglyceridemia.
If your triglycerides are too high it sounds like it may be your low-fat diet that is to blame.
When we eat carbs our body burns the carbs in preference to dietary (and body) fat and stores the dietary fat very efficiently. If we do this in excess for too long we get fat.