Tuesday, March 4, 2014
At least this was the finding in an overfeeding study conducted by Fredrik Rosqvist and colleagues from the Uppsala University, Sweden, published in DIABETES.
The study with the memorable acronym LIPOGAIN, was a double-blind, parallel-group, randomized trial involving 39 young normal-weight individuals who were overfed muffins either high in saturated fats (palm oil) or in n-6 poly-unsaturated fats (sunflower oil) for seven weeks.
The number of muffins that each subject had to consume were individually adjusted to ensure that each subject increased their body weight by about 1.5 Kg (or 3%). To achieve this, the subjects consumed on average three muffins or about an extra 750 kcals/day.
However, where the excess calories went was quite different.
While the subjects eating saturated fat markedly increased their liver fat and gained almost twice as much visceral fat as those in the poly-unsaturated fat group, the latter experienced a nearly three-fold larger increase in lean tissue than the saturated fat group.
The two diets also had quite different effects on the expression of genes regulating energy dissipation, insulin resistance, body composition and fat cell differentiation in subcutaneous fat tissue.
Thus, the authors conclude that while overeating saturated fat promotes liver and visceral fat storage, the excess energy from poly-unsaturated fat may instead promote the growth of lean tissue.
What I learnt from this study is that there are indeed important differences in how the body handles excess calories depending on where they come from.
In that respect at least, not all calories are equal.
Rosqvist F, Iggman D, Kullberg J, Jonathan Cedernaes J, Johansson HE, Larsson A, Johansson L, Ahlström H, Arner P, Dahlman I, & Risérus U (2014). Overfeeding Polyunsaturated and Saturated Fat Causes Distinct Effects on Liver and Visceral Fat Accumulation in Humans. Diabetes PMID: 24550191