Your cells need several types of biochemical compounds in relatively large amounts to provide for cellular energy and nutritional needs. These compounds are collectively called macronutrients. Triglycerides are a kind of fat, and are one of the macronutrients. A second macronutrient category is carbohydrate, of which glucose is a member.
Human Nutrition
Humans need macronutrients -- fats, carbohydrates, and proteins -- and micronutrients, which include vitamins and minerals, in order to stay healthy. Triglycerides are storage fats, and you consume them any time you eat animal fat or plant oil. Glucose is a kind of carbohydrate. It's found in both sugars and starches, and you consume it any time you eat anything either sweet or starchy. Your cells use both triglycerides and glucose for energy.
Energy Content
Triglycerides contain more energy per unit mass than glucose and other carbohydrates do. This is one of the reasons that fat is so calorically dense compared to carbohydrate. Triglycerides provide nine calories of energy per gram consumed, while glucose and other carbohydrates provide only four calories of energy per gram, explains Dr. Lauralee Sherwood in her book "Human Physiology." The energy density of triglyceride is further increased by the fact that fat typically doesn't have much water in it, while carbohydrate-containing foods do.
Digestion and Absorption
When you consume triglycerides, enzymes called lipases break the triglycerides into smaller molecules. Your intestine absorbs these and reassembles them, and they are then released into the bloodstream so that cells can take them up. When you eat glucose-containing carbohydrate foods, including sugar and starch, various enzymes break the carbohydrates into glucose and other similar molecules, explains Dr. Gary Thibodeau in his book "Anatomy and Physiology." Your intestine then absorbs the glucose and other molecules into the bloodstream.
Cellular Use
Your cells can burn either triglyceride or glucose for immediate energy, or can store either of them for later use. Some cells burn glucose preferentially over triglyceride -- the brain, for instance, doesn't utilize fat, but does use a significant quantity of the glucose you eat each day. Dr. Sherwood further notes that your body can convert excess glucose into triglyceride, so you can store it as fat, but you can't convert fat -- whether ingested or stored -- into glucose.
Expert Insight
Overconsumption of both triglyceride and glucose leads to excess weight gain. If you consume too much fat, you store it as body fat. If you consume too much sugar, you convert it to body fat and store it. As a result, overconsumption of either triglyceride or glucose can lead to health effects, including type 2 diabetes, that are associated with obesity. Because fat contains more calories per gram, many individuals interested in losing body fat limit dietary fat, but you have to limit both fat and sources of glucose in order to avoid storing too much body fat.
References
- "Human Physiology"; Lauralee Sherwood, Ph.D.; 2004
- "Anatomy and Physiology"; Gary Thibodeau, Ph.D.; 2007
