YOU FEEL EXHAUSTED – MOST OF THE TIME…
This is not how you should feel, and it’s definitely not how you want to feel
Tiredness can come from many different sources. So it's vitally important to understand if it is your diet… or something else
To help you find an answer, answer these more specific questions about your diet and see which category (if any) you fall into.
Then read what you can do about it
This question has two parts to it – “Am I getting enough calories (energy) in my diet?” and “Am I getting enough of the essential nutrients in my diet?”
Simply put – your weight will tell you whether you are eating enough calories. If you are maintaining a normal weight , then this is not your problem. If you are under or over weight then this may need adjusting.
Your calorie intake needs to be in balance, or you will start to feel tired.
As a guide, an average need for women is 1,800 to 2,000 calories per day and for men 2,500 calories.
NOTE – Details on the link between being overweight and tired are here
If you have a balanced diet then you will be getting the right nutrients. But it is increasingly common (especially among young people) to be getting too many calories and not enough of the good stuff.
In a nutshell it is a good idea to watch the amount of sugar you are eating – or drinking. You can do this by taking note of the guide which is printed on all food wrappers.
Are you a snacker or a gorger?
There seems to be some controversy about what’s best.
On the one hand our grandparents did very well on 3 meals a day. They had far less obesity and lower incidences of malnutrition. Yet there are people who swear by 5 or 6 small meals a day to keep the blood sugar level.
Science says that our genetic heritage points to a lifestyle of feast or famine. Whether our genes evolved to favor the 3 meals a day pattern is still open to debate.
However, recent compelling research shows that children who miss breakfast, or who have only sugary snacks for breakfast do less well in the late school morning.
A review of 19 recent studies which examined the effects of breakfast on behavior in children and adolescents was done. They found that 11 studies showed a positive effect of breakfast on behavior in the classroom. 
So although there is relatively little evidence confirming or denying theories on how often we should eat, missing the odd meal usually has very little effect.
However, if the gap between meals is over about 6 hours, our blood sugar levels become low, which can make us tired and irritable. (Another reason why breakfast is important after the overnight fast.)
If for some reason you can’t face food in the morning, take a healthy snack with you to eat at a mid-morning break. For shift workers this may be even more important.
I’m sure you’ve heard that energy drinks and foods with a lot of sugar in them can cause tiredness…
But what is the science behind it?
An influx of sugar raises your blood sugar level for a short period of time… then lowers it.
And your blood sugar level is what gives you energy
The chart shows how the levels of blood sugar change after a high sugar meal in red and a low sugar one in green.
As you can see, some foods are absorbed slowly, take longer to digest and give you energy for longer. Food and drinks high in sugar are quickly absorbed and give you energy fast, but quickly pass through your system.
If the values of our blood sugar dip, we are likely to feel weary. E.g. the mid- afternoon slump is often related to low blood sugar.
A sugar doughnut mid -afternoon will give you a burst of energy – but it won’t last long and soon you will feel drained again. Better to have a handful of unsalted nuts or oatcakes to keep you going till dinner time. Their energy will burn slower resulting in no ‘come down’ and tiredness.
Certain classes of foods may help in giving energy over a period of time. Proteins taken at breakfast time take a while to digest, so together with low GI carbohydrates they can keep you energized for hours.
A quick fix may use a sugary drink or sweets – but the effects are short-lived. A plate of pasta as an evening meal can make you feel sleepy – as can – oddly enough – lettuce. Lettuce contains ‘lactur carium' which has a sedating effect on the nervous system. It's been recognized to help sleep since at least the Elizabethan times.
Most of us know that “after feast” feeling, when all we want to do is just to sit back and do nothing.
Your body needs time to absorb a heavy meal. It tells you this by draining your energy, and making you feel tired.
Biologically your body is sending all its energy to aid digestion. Taking it from your brain leaving you feeling tired.
An easy way to regulate your portion size and type of food is illustrated in this YouTube video: (it lasts just 2.42minutes)
In short, portion size is often overlooked and can be real cause of excess tiredness
Eating too much at a sitting means your body has to focus on digesting the food you just ate. Rather than provide you the energy to do what you need to.
A healthy and well balanced diet, eaten in moderation, will not cause you to feel tired.
Some diets, especially some weight loss diets may be deficient in certain essential nutrients – and then you will feel tired – your body is trying to tell you something. Also, at certain times of day, missing too many meals, or about an hour after eating high sugar foods you may have feelings of temporary fatigue and lassitude.
Many people find that adjusting their diets, choosing healthy options and moderate portions gives them a feeling of alertness of having more energy – it’s just a matter of taste.
Thanks for reading this guide, I hope it has helped answer the question ‘Is my diet making me tired?' You can get more information on other reasons you might be feeling tired here
 Elizabeth J Parks and Megan A McCrory When to eat and how often? 2005 American Society for Clinical Nutrition