Thank you for the information on which bars don't have sugar alcohols because they do upset my digestion.

Glycerol is used as a substrate in clinical studies when there is need for a poor gluconeogenic substrate. Glycerol has been shown to suppress appetite.

Int J Vitam Nutr Res 1979;49(3):317-21

Metabolic studies in rats under glucose and glycerol loading.

Om P, Hohenegger M.

It has been found in rats that 40% glycerol, when added to standard diet, reduces the food intake and thus prevents weight gain. The subcutaneous application (40 mg/kg three times daily) has no effect. Under pair feeding conditions the oxygen consumption, the RQ value and body weight remain unaffected as compared with controls receiving glucose. It is concluded that reduction of body weight induced by glycerol feeding is due to reduced amount of food intake and not due to any alterations of energy metabolism.
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This was an interesting article on glycerin showing that putting an IV of straight glycerin into an infant did not change glucose levels:

Acta Biol Med Ger 1977;36(9):1289-98

[Absorption and metabolism of glycerin in the neonatal period. I. Speed of turnover of glycerin during continuous intravenous infusions in newborn infants of various gestational ages and in older infants]

[Article in German]

Reich J, Beyreiss K, Scheerschmidt G, Willgerodt H, Melichar V.

Glycerol was infused intravenously over 2 hours in preterm and term appropriate-for-date and in term small-for-date infants at the age of 12 to 72 hours and 10 to 14 days and in infants at the age of 3 to 8 months. The dosage was 0.25.kg-1.h-1 and 0.5.kg-1.h-1, respectively. Less than 6 per cent of the glycerol injused were recovered in the urine irrespective of the dosage. The total clearance was 9.1 to 14.6 ml.kg-1. min-1 during the first weeks of life with 0.25 g.kg-1.h-1 glycerol irrespective of gestational age and intra-uterine growth retardation; and it rose to 31.8 ml.kg-1.min-1 in older infants. With 0.5.kg-1.h-1 glycerol the total clearance values were lower in all groups. The glucose blood level and the blood lactate concentration as well as the parameters of the acid-base-balance were not significantly influenced by glycerol.