The average American consumes 56 pounds of added sugar per year, wrote David DiSalvo, in the Forbes.com article "What Eating Too Much Sugar Does to Your Brain." That equals about 27.5 teaspoons of sugar a day -- or 440 calories. All this sugar means you have less room for healthy foods that supply solid nutrition, like vegetables, fruits, proteins and whole grains. The sugar overload can also prevent you from feeling your best. The negative effects can be immediate, or long term.
Pediatric specialist Dr. Robert Lustig, has called sugar toxic because of the effects it can have on your body. When you consume refined sugar, a combination of fructose and glucose, your liver must work harder than it does when you consume a starch, which consists of glucose alone. Liquid forms of sugar hit your system even more quickly than solid foods, especially whole natural foods such as fruit. If you're overloading your system with high doses of sugar, your liver coverts a lot of the calories to fat. Over time, this leads to a condition called insulin resistance in which your body inefficiently burns calories and stores too high a proportion as fat, causing weight gain and possibly putting you at risk of type 2 diabetes and cancer. Carrying too much weight and being in a constant state of inflammation because of consuming too much sugar will certainly make you feel poorly.
Crash and Burn
Sugar provides you with an instant surge of energy, but it isn't long lasting. Once your blood sugar surges to respond to the sugar influx and your metabolism burns through it, your system crashes and you end up dragging. Extreme highs and lows experienced after eating sugar could signal a sugar sensitivity or a prediabetic state, so it's important to mention these symptoms to your doctor.
Too much sugar affects your brain as well as your body. A high-sugar diet causes your brain to produce less of a brain chemical called brain-derived neurotrophic factor, or BDNF, which helps with memory formation and learning. If you feel foggy headed after eating sugar, you may be experiencing the effect of diminished levels of BDNF.
Just Can't Get Enough
You may feel poorly after eating sugar because your fullness sensors become impaired. As a result, you may end up eating more than your body needs and then feel uncomfortably full and sluggish. A study published in a 2010 issue of "Peptides" found that chronic consumption of sugar dampens the signals in your body that indicate satiation and that leads to overeating.