Triglycerides contain more metabolic energy per unit weight than glycogen because:
i. glycogen has greater polarity than fatty acids.
ii. fatty acids predominate in an anhydrous form
iii. fatty acids are less oxidized than carbohydrates.
iv. triglycerides have a higher average molecular mass.

III. Fatty acids are less oxidized than carbohydrates

Explanation:

Both triglycerides and glycogen may be used to obtain energy, this is:

-Triglycerides through the B-oxidation, where a molecule is first activated and entered into mitochondria matrix, to be degraded (oxidized)

-Glycolysis, where a molecule of 6 carbons is splitted in 2 components of 3 carbons each (pyruvate)

As an energy reserve substance, triglycerides have 2 main advantages, compared with glycogen:

1)From the chemical point of view, triglycerides have a more reduced state than glycogen (this is, have more atoms of hydrogens), hence these molecules give twice energy than glycogen

2)As triglycerides are hydrophobic molecules, they remain in an anhydrous form (unlike glycogen, which is hydrophilic), and this makes easier to move these molecules to obtain energy  

the formula would be mgso4

mgso[subscript]4